{"id":74151,"date":"2024-07-08T18:00:49","date_gmt":"2024-07-08T11:00:49","guid":{"rendered":"https:\/\/itviec.com\/blog\/?p=74151"},"modified":"2025-10-12T00:10:34","modified_gmt":"2025-10-11T17:10:34","slug":"join-trong-sql","status":"publish","type":"post","link":"https:\/\/itviec.com\/blog\/join-trong-sql\/","title":{"rendered":"JOIN trong SQL: C\u00fa ph\u00e1p v\u00e0 c\u00e1ch s\u1eed d\u1ee5ng c\u00e1c ph\u00e9p JOIN"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_85 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">N\u1ed9i dung b\u00e0i vi\u1ebft<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/itviec.com\/blog\/join-trong-sql\/#Phep_JOIN_trong_SQL_la_gi\" >Ph\u00e9p JOIN trong SQL l\u00e0 g\u00ec?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/itviec.com\/blog\/join-trong-sql\/#Cac_loai_JOIN_trong_SQL\" >C\u00e1c lo\u1ea1i JOIN trong SQL<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/itviec.com\/blog\/join-trong-sql\/#DELETE_JOIN_la_gi\" >DELETE JOIN l\u00e0 g\u00ec?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/itviec.com\/blog\/join-trong-sql\/#Cau_hoi_thuong_gap_ve_cach_su_dung_JOIN_trong_SQL\" >C\u00e2u h\u1ecfi th\u01b0\u1eddng g\u1eb7p v\u1ec1 c\u00e1ch s\u1eed d\u1ee5ng JOIN trong SQL<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/itviec.com\/blog\/join-trong-sql\/#Tong_ket_cach_su_dung_JOIN_trong_SQL\" >T\u1ed5ng k\u1ebft c\u00e1ch s\u1eed d\u1ee5ng JOIN trong SQL<\/a><\/li><\/ul><\/nav><\/div>\n\n<p><em><strong>Ph\u00e9p JOIN trong SQL l\u00e0 c\u00f4ng c\u1ee5 m\u1ea1nh m\u1ebd gi\u00fap k\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb nhi\u1ec1u b\u1ea3ng, x\u00e2y d\u1ef1ng c\u00e1i nh\u00ecn to\u00e0n di\u1ec7n v\u00e0 ch\u00ednh x\u00e1c v\u1ec1 th\u00f4ng tin. Trong l\u0129nh v\u1ef1c d\u1eef li\u1ec7u, vi\u1ec7c k\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb nhi\u1ec1u b\u1ea3ng l\u00e0 r\u1ea5t quan tr\u1ecdng \u0111\u1ec3 c\u00f3 \u0111\u01b0\u1ee3c b\u1ee9c tranh t\u1ed5ng th\u1ec3. Trong b\u00e0i vi\u1ebft n\u00e0y, ch\u00fang ta s\u1ebd kh\u00e1m ph\u00e1 s\u00e2u h\u01a1n v\u1ec1 c\u00e1c ph\u00e9p JOIN.<\/strong><\/em><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">\u0110\u1ecdc b\u00e0i vi\u1ebft n\u00e0y \u0111\u1ec3 hi\u1ec3u v\u1ec1:<\/span><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><span style=\"font-weight: 400;\">C\u00e1c ph\u00e9p JOIN trong SQL<\/span><\/li>\n\n\n\n<li><span style=\"font-weight: 400;\">C\u00fa ph\u00e1p v\u00e0 c\u00e1ch s\u1eed d\u1ee5ng c\u00e1c ph\u00e9p JOIN<\/span><\/li>\n\n\n\n<li><span style=\"font-weight: 400;\">DELETE JOIN l\u00e0 g\u00ec?<\/span><\/li>\n<\/ul>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>Xem th\u00eam: <a href=\"https:\/\/itviec.com\/viec-lam-it\/sql?utm_medium=anchor_text_high&amp;utm_source=blog&amp;utm_campaign=viec_lam_sql&amp;utm_content=join_trong_sql\" target=\"_blank\" rel=\"noreferrer noopener\">Vi\u1ec7c l\u00e0m SQL<\/a> n\u1ed5i b\u1eadt tr\u00ean ITviec<\/strong><\/p>\n<\/blockquote>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-phep-join-trong-sql-la-gi\"><span class=\"ez-toc-section\" id=\"Phep_JOIN_trong_SQL_la_gi\"><\/span><b>Ph\u00e9p JOIN trong SQL l\u00e0 g\u00ec?<\/b><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p><span style=\"font-weight: 400;\">Ph\u00e9p JOIN (n\u1ed1i) l\u00e0 m\u1ed9t trong nh\u1eefng ch\u1ee9c n\u0103ng quan tr\u1ecdng trong SQL, cho ph\u00e9p ng\u01b0\u1eddi d\u00f9ng k\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb hai ho\u1eb7c nhi\u1ec1u b\u1ea3ng kh\u00e1c nhau trong c\u00f9ng m\u1ed9t c\u01a1 s\u1edf d\u1eef li\u1ec7u ch\u1ec9 v\u1edbi 1 c\u00e2u truy v\u1ea5n.<\/span><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">N\u00f3 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng khi c\u1ea7n truy v\u1ea5n d\u1eef li\u1ec7u t\u1eeb nhi\u1ec1u b\u1ea3ng \u0111\u1ec3 tr\u1ea3 v\u1ec1 k\u1ebft qu\u1ea3 trong c\u00f9ng m\u1ed9t t\u1eadp d\u1eef li\u1ec7u. Hai b\u1ea3ng c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c k\u1ebft n\u1ed1i v\u1edbi nhau khi c\u00f3 m\u1ed9t tr\u01b0\u1eddng chung gi\u1eefa hai b\u1ea3ng n\u00e0y (th\u01b0\u1eddng l\u00e0 kh\u00f3a ch\u00ednh v\u00e0 kh\u00f3a ngo\u1ea1i).<\/span><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">Trong tr\u01b0\u1eddng h\u1ee3p c\u1ea7n k\u1ebft n\u1ed1i nhi\u1ec1u h\u01a1n hai b\u1ea3ng, c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng nhi\u1ec1u ph\u00e9p JOIN d\u1ef1a tr\u00ean c\u00f9ng c\u01a1 ch\u1ebf nh\u01b0 khi k\u1ebft n\u1ed1i hai b\u1ea3ng.<\/span><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">Ph\u00e9p JOIN gi\u00fap t\u1ed1i \u01b0u h\u00f3a qu\u00e1 tr\u00ecnh truy v\u1ea5n d\u1eef li\u1ec7u, cho ph\u00e9p truy c\u1eadp th\u00f4ng tin t\u1eeb nhi\u1ec1u b\u1ea3ng m\u1ed9t c\u00e1ch d\u1ec5 d\u00e0ng v\u00e0 l\u00e0 m\u1ed9t c\u00f4ng c\u1ee5 m\u1ea1nh m\u1ebd cho c\u00e1c nh\u00e0 ph\u00e2n t\u00edch d\u1eef li\u1ec7u, l\u1eadp tr\u00ecnh vi\u00ean v\u00e0 b\u1ea5t k\u1ef3 ai c\u1ea7n truy v\u1ea5n d\u1eef li\u1ec7u t\u1eeb c\u00e1c b\u1ea3ng kh\u00e1c nhau.<\/span><\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><em>T\u00ecm hi\u1ec3u th\u00eam v\u1ec1 <a href=\"https:\/\/itviec.com\/blog\/sql-database-la-gi\/\" target=\"_blank\" rel=\"noopener\"><strong>SQL Database \u2013 Ng\u00f4n ng\u1eef truy v\u1ea5n m\u1ea1nh m\u1ebd cho c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/strong><\/a><\/em><\/p>\n<\/blockquote>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-cac-lo\u1ea1i-join-trong-sql\"><span class=\"ez-toc-section\" id=\"Cac_loai_JOIN_trong_SQL\"><\/span><b>C\u00e1c lo\u1ea1i JOIN trong SQL<\/b><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p><span style=\"font-weight: 400;\">Tr\u01b0\u1edbc h\u1ebft, c\u00f9ng xem x\u00e9t 3 b\u1ea3ng d\u1eef li\u1ec7u sau:<\/span><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><span style=\"font-weight: 400;\">B\u1ea3ng A: Customer (Kh\u00e1ch h\u00e0ng)<\/span><\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Customer_id<\/td><td>Name<\/td><td>City<\/td><\/tr><tr><td>1<\/td><td>Alice<\/td><td>New York<\/td><\/tr><tr><td>2<\/td><td>Bob<\/td><td>Los Angeles<\/td><\/tr><tr><td>3<\/td><td>Charlie<\/td><td>Chicago<\/td><\/tr><tr><td>4<\/td><td>David<\/td><td>Miami<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<ul class=\"wp-block-list\">\n<li><span style=\"font-weight: 400;\">B\u1ea3ng B: Order (\u0110\u01a1n h\u00e0ng)<\/span><\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Order_id<\/td><td>Customer_id<\/td><td>Product_id<\/td><td>Price<\/td><\/tr><tr><td>101<\/td><td>1<\/td><td>1<\/td><td>1000<\/td><\/tr><tr><td>102<\/td><td>2<\/td><td>2<\/td><td>800<\/td><\/tr><tr><td>103<\/td><td>1<\/td><td>3<\/td><td>500<\/td><\/tr><tr><td>104<\/td><td>3<\/td><td>4<\/td><td>200<\/td><\/tr><tr><td>105<\/td><td>5<\/td><td>5<\/td><td>300<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<ul class=\"wp-block-list\">\n<li><span style=\"font-weight: 400;\">B\u1ea3ng C: Product (S\u1ea3n ph\u1ea9m)<\/span><\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><b>Product_id<\/b><\/td><td><b>Product_name<\/b><\/td><td><b>Category<\/b><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">1<\/span><\/td><td><span style=\"font-weight: 400;\">Laptop<\/span><\/td><td><span style=\"font-weight: 400;\">Electronics<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">2<\/span><\/td><td><span style=\"font-weight: 400;\">Smartphone<\/span><\/td><td><span style=\"font-weight: 400;\">Electronics<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">3<\/span><\/td><td><span style=\"font-weight: 400;\">Tablet<\/span><\/td><td><span style=\"font-weight: 400;\">Electronics<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">4<\/span><\/td><td><span style=\"font-weight: 400;\">Headphones<\/span><\/td><td><span style=\"font-weight: 400;\">Accessories<\/span><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>Ch\u00fang ta s\u1ebd s\u1eed d\u1ee5ng c\u00e1c b\u1ea3ng d\u1eef li\u1ec7u n\u00e0y trong c\u00e1c v\u00ed d\u1ee5 v\u1ec1 c\u00e1c ph\u00e9p JOIN d\u01b0\u1edbi \u0111\u00e2y:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-inner-join\"><b>Inner Join<\/b><\/h3>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"780\" height=\"464\" src=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-inner-vippro.jpg\" alt=\"join trong sql - inner join\" class=\"wp-image-74161\" srcset=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-inner-vippro.jpg 780w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-inner-vippro-300x178.jpg 300w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-inner-vippro-700x416.jpg 640w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-inner-vippro-200x119.jpg 200w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-inner-vippro-100x59.jpg 100w\" sizes=\"auto, (max-width: 780px) 100vw, 780px\" \/><\/figure>\n\n\n\n<ul class=\"wp-block-list\">\n<li><b>C\u00fa ph\u00e1p 1<\/b><span style=\"font-weight: 400;\">:<\/span><\/li>\n<\/ul>\n\n\n\n<p><span style=\"font-weight: 400;\">INNER JOIN l\u00e0 m\u1ed9t l\u1ec7nh \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 k\u1ebft h\u1ee3p c\u00e1c h\u00e0ng t\u1eeb c\u1ea3 hai b\u1ea3ng th\u1ecfa m\u00e3n \u0111i\u1ec1u ki\u1ec7n cho tr\u01b0\u1edbc. S\u1eed d\u1ee5ng INNER JOIN s\u1ebd tr\u1ea3 v\u1ec1 nh\u1eefng h\u00e0ng c\u00f3 gi\u00e1 tr\u1ecb kh\u1edbp nhau trong c\u1ea3 hai b\u1ea3ng. \u0110i\u1ec1u n\u00e0y c\u00f3 ngh\u0129a l\u00e0 ch\u1ec9 nh\u1eefng h\u00e0ng t\u1eeb m\u1ed7i b\u1ea3ng ph\u00f9 h\u1ee3p v\u1edbi \u0111i\u1ec1u ki\u1ec7n \u0111\u01b0\u1ee3c li\u00ean k\u1ebft m\u1edbi \u0111\u01b0\u1ee3c xu\u1ea5t hi\u1ec7n trong k\u1ebft qu\u1ea3 truy v\u1ea5n. \u0110\u00e2y l\u00e0 lo\u1ea1i JOIN \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng ph\u1ed5 bi\u1ebfn nh\u1ea5t v\u00e0 \u0111\u01b0\u1ee3c coi l\u00e0 thao t\u00e1c JOIN m\u1eb7c \u0111\u1ecbnh.<\/span><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> columns&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> tableA&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">INNER<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> tableB&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> tableA.column = tableB.column;<\/span><\/code><\/pre>\n\n\n\n<p><span style=\"font-weight: 400;\">Trong \u0111\u00f3:<\/span><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><span style=\"font-weight: 400;\"><strong>SELECT columns<\/strong>: Li\u1ec7t k\u00ea c\u00e1c c\u1ed9t m\u00e0 b\u1ea1n mu\u1ed1n l\u1ea5y d\u1eef li\u1ec7u.<\/span><\/li>\n\n\n\n<li><span style=\"font-weight: 400;\"><strong>FROM tableA<\/strong>: Ch\u1ec9 \u0111\u1ecbnh b\u1ea3ng c\u01a1 s\u1edf t\u1eeb \u0111\u00f3 b\u1ea1n mu\u1ed1n l\u1ea5y d\u1eef li\u1ec7u.<\/span><\/li>\n\n\n\n<li><span style=\"font-weight: 400;\"><strong>INNER JOIN tableB<\/strong>: Ch\u1ec9 \u0111\u1ecbnh b\u1ea3ng m\u00e0 b\u1ea1n mu\u1ed1n k\u1ebft h\u1ee3p v\u1edbi b\u1ea3ng c\u01a1 s\u1edf (b\u1edfi v\u00ec inner join \u0111\u01b0\u1ee3c xem l\u00e0 ph\u00e9p JOIN m\u1eb7c \u0111\u1ecbnh n\u00ean ch\u00fang ta c\u00f3 th\u1ec3 vi\u1ebft g\u1ecdn l\u00e0 JOIN table B)<\/span><\/li>\n\n\n\n<li><span style=\"font-weight: 400;\"><strong>ON tableA.column = tableB.column<\/strong>: Ch\u1ec9 \u0111\u1ecbnh \u0111i\u1ec1u ki\u1ec7n \u0111\u1ec3 k\u1ebft h\u1ee3p c\u00e1c h\u00e0ng t\u1eeb hai b\u1ea3ng.<\/span><\/li>\n<\/ul>\n\n\n\n<p><b>V\u00ed d\u1ee5<\/b><span style=\"font-weight: 400;\">: <\/span><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">\u0110\u1ec3 l\u1ea5y th\u00f4ng tin c\u1ee7a kh\u00e1ch h\u00e0ng v\u00e0 \u0111\u01a1n h\u00e0ng c\u1ee7a h\u1ecd, ta th\u1ef1c hi\u1ec7n ph\u00e9p k\u1ebft n\u1ed1i INNER JOIN nh\u01b0 sau:<\/span><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> Customers.name, Customers.City, Orders.Order_id, Orders.Product_name, Orders.Price&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> Customers&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">INNER<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> Orders&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> Customers.Customer_id = Orders.Customer_id;<\/span><\/code><\/pre>\n\n\n\n<p><strong>B\u1ea3ng k\u1ebft qu\u1ea3:<\/strong><span style=\"font-weight: 400;\"><br><\/span><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>\n<p style=\"text-align: left;\"><b>Name<\/b><\/p>\n<\/td><td><b>City<\/b><\/td><td><b>Order_id<\/b><\/td><td><b>Product_name<\/b><\/td><td><b>Price<\/b><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Alice<\/span><\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">101<\/span><\/td><td><span style=\"font-weight: 400;\">Laptop<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">1000<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Alice<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">103<\/span><\/td><td><span style=\"font-weight: 400;\">Tablet<\/span><\/td><td><span style=\"font-weight: 400;\">500<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Bob<\/span><\/td><td><span style=\"font-weight: 400;\">Los Angeles<\/span><\/td><td><span style=\"font-weight: 400;\">102<\/span><\/td><td><span style=\"font-weight: 400;\">Smartphone<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">800<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Charlie<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Chicago<\/span><\/td><td><span style=\"font-weight: 400;\">104<\/span><\/td><td><span style=\"font-weight: 400;\">Headphones<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">200<\/span><\/p>\n<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p><b>Gi\u1ea3i th\u00edch:<\/b><span style=\"font-weight: 400;\"> INNER JOIN tr\u1ea3 v\u1ec1 c\u00e1c h\u00e0ng c\u00f3 gi\u00e1 tr\u1ecb kh\u1edbp gi\u1eefa b\u1ea3ng Customers v\u00e0 Orders d\u1ef1a tr\u00ean \u0111i\u1ec1u ki\u1ec7n JOIN l\u00e0 Customer_id gi\u1eefa 2 b\u1ea3ng ph\u1ea3i gi\u1ed1ng nhau. H\u00e0ng kh\u00f4ng th\u1ecfa m\u00e3n \u0111i\u1ec1u ki\u1ec7n JOIN (nh\u01b0 Customer_id = 5 trong b\u1ea3ng Orders) s\u1ebd kh\u00f4ng xu\u1ea5t hi\u1ec7n trong k\u1ebft qu\u1ea3.<\/span><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><b>C\u00fa ph\u00e1p 2<\/b><span style=\"font-weight: 400;\">: B\u00ean c\u1ea1nh c\u00fa ph\u00e1p INNER JOIN th\u00f4ng th\u01b0\u1eddng, ta c\u0169ng c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng c\u00fa ph\u00e1p kh\u00e1c b\u1eb1ng c\u00e1ch li\u1ec7t k\u00ea c\u00e1c b\u1ea3ng c\u1ea7n k\u1ebft h\u1ee3p v\u00e0 \u0111i\u1ec1u ki\u1ec7n k\u1ebft h\u1ee3p trong ph\u1ea7n WHERE. C\u00fa ph\u00e1p n\u00e0y gi\u00fap vi\u1ebft c\u00e2u l\u1ec7nh truy v\u1ea5n SQL m\u1ed9t c\u00e1ch ng\u1eafn g\u1ecdn h\u01a1n m\u00e0 v\u1eabn \u0111\u1ea3m b\u1ea3o k\u1ebft qu\u1ea3 t\u01b0\u01a1ng \u0111\u01b0\u01a1ng.<\/span><\/li>\n<\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> columns&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> tableA, tableB<\/span>\n\n<span style=\"font-weight: 400;\">WHERE<\/span><span style=\"font-weight: 400;\"> tableA.column = tableB.column;<\/span><\/code><\/pre>\n\n\n\n<ul class=\"wp-block-list\">\n<li><b>C\u00fa ph\u00e1p 3<\/b><span style=\"font-weight: 400;\">: Ngo\u00e0i ra, c\u00fa ph\u00e1p JOIN c\u00f3 th\u1ec3 k\u1ebft h\u1ee3p v\u1edbi \u0111i\u1ec1u ki\u1ec7n ph\u1ee9c t\u1ea1p h\u01a1n cho ph\u00e9p k\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb hai b\u1ea3ng d\u1ef1a tr\u00ean m\u1ed9t ho\u1eb7c nhi\u1ec1u \u0111i\u1ec1u ki\u1ec7n logic.\u00a0<\/span><\/li>\n<\/ul>\n\n\n\n<p><span style=\"font-weight: 400;\">\u0110\u1ec3 vi\u1ebft c\u00e2u truy v\u1ea5n SQL m\u00e0 t\u1ea5t c\u1ea3 c\u00e1c \u0111i\u1ec1u ki\u1ec7n \u0111\u1ec1u ph\u1ea3i th\u1ecfa m\u00e3n ta s\u1ebd s\u1eed d\u1ee5ng AND:<\/span><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> columns&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> tableA&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">INNER<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> tableB <\/span><span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> tableA.column = tableB.column<\/span>\n\n<span style=\"font-weight: 400;\">AND &lt;\u0110i\u1ec1u ki\u1ec7n&gt;<\/span><\/code><\/pre>\n\n\n\n<p><span style=\"font-weight: 400;\">Ho\u1eb7c n\u1ebfu mu\u1ed1n ch\u1ecdn c\u00e1c b\u1ea3n ghi th\u1ecfa m\u00e3n \u00edt nh\u1ea5t m\u1ed9t trong c\u00e1c \u0111i\u1ec1u ki\u1ec7n, ta s\u1ebd s\u1eed d\u1ee5ng OR :<\/span><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> columns&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> tableA&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">INNER<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> tableB <\/span><span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> tableA.column = tableB.column<\/span>\n\n<span style=\"font-weight: 400;\">OR &lt;\u0110i\u1ec1u ki\u1ec7n&gt;<\/span><\/code><\/pre>\n\n\n\n<p><span style=\"font-weight: 400;\"><strong>V\u00ed d\u1ee5:<\/strong> <\/span><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">\u0110\u1ec3 l\u1ea5y th\u00f4ng tin t\u1eeb b\u1ea3ng Customers v\u00e0 Orders m\u00e0 th\u1ecfa m\u00e3n \u0111i\u1ec1u ki\u1ec7n kh\u00e1ch h\u00e0ng c\u00f3 \u0111\u01a1n h\u00e0ng v\u1edbi gi\u00e1 l\u1edbn h\u01a1n 500, ta vi\u1ebft c\u00e2u truy v\u1ea5n nh\u01b0 sau:<\/span><span style=\"font-weight: 400;\"><br><\/span><span style=\"font-weight: 400;\">SELECT<\/span> <span style=\"font-weight: 400;\">Customers.Customer_id, Customers.Name, Customers.City, Orders.Product_name, Orders.Price<\/span><span style=\"font-weight: 400;\">&nbsp;<\/span><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> Customers&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">INNER<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> Orders&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> Customers.Customer_Id = Orders.Customer_id&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">AND<\/span><span style=\"font-weight: 400;\"> Orders.Price &gt; <\/span><span style=\"font-weight: 400;\">500<\/span><span style=\"font-weight: 400;\">;<\/span><\/code><\/pre>\n\n\n\n<p><strong>B\u1ea3ng k\u1ebft qu\u1ea3:<\/strong><span style=\"font-weight: 400;\"><br><\/span><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>\n<p style=\"text-align: left;\"><b>Customer_id<\/b><\/p>\n<\/td><td><b>Name<\/b><\/td><td><b>City<\/b><\/td><td><b>Product_name<\/b><\/td><td><b>Price<\/b><\/td><\/tr><tr><td>\n<p style=\"text-align: left;\">1<\/p>\n<\/td><td>Alice<\/td><td>New York<\/td><td>Laptop<\/td><td>1000<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\">2<\/p>\n<\/td><td>Bob<\/td><td>Los Angeles<\/td><td>Smartphone<\/td><td>\n<p style=\"text-align: left;\">800<\/p>\n<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<ul class=\"wp-block-list\">\n<li><b>C\u00fa ph\u00e1p 4<\/b><span style=\"font-weight: 400;\">: C\u00fa ph\u00e1p JOIN ba b\u1ea3ng t\u01b0\u01a1ng t\u1ef1 nh\u01b0 c\u00fa ph\u00e1p JOIN hai b\u1ea3ng, nh\u01b0ng t\u0103ng s\u1ed1 l\u01b0\u1ee3ng INNER JOIN l\u00ean. \u0110i\u1ec1u ki\u1ec7n l\u00e0 ph\u1ea3i c\u00f3 m\u1ed9t b\u1ea3ng c\u00f3 c\u1ed9t kh\u1edbp v\u1edbi hai b\u1ea3ng c\u00f2n l\u1ea1i. \u0110i\u1ec1u n\u00e0y \u0111\u1ea3m b\u1ea3o r\u1eb1ng ch\u00fang ta c\u00f3 th\u1ec3 li\u00ean k\u1ebft t\u1ea5t c\u1ea3 c\u00e1c b\u1ea3ng l\u1ea1i v\u1edbi nhau d\u1ef1a tr\u00ean c\u00e1c c\u1ed9t chung.<\/span><\/li>\n<\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> columns&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> tableA&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">INNER<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> tableB <\/span><span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> tableA.column = tableB.column&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">INNER<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> tableC <\/span><span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> tableB.column = tableC.column;<\/span><\/code><\/pre>\n\n\n\n<p><span style=\"font-weight: 400;\"><strong>V\u00ed d\u1ee5:<\/strong> <\/span><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">\u0110\u1ec3 l\u1ea5y th\u00f4ng tin kh\u00e1ch h\u00e0ng v\u1edbi \u0111\u01a1n h\u00e0ng v\u00e0 danh m\u1ee5c h\u00e0ng ho\u00e1 t\u01b0\u01a1ng \u1ee9ng, ta th\u1ef1c hi\u1ec7n ph\u00e9p INNER JOIN nh\u01b0 sau:<\/span><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> Customer.Customer_id, Customer.Name, Customer.City, Orders.Order_id, Orders.Product_name, Orders.Price, Products.Category<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> Customer<\/span>\n\n<span style=\"font-weight: 400;\">INNER JOIN<\/span><span style=\"font-weight: 400;\"> Orders <\/span><span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> Customer.Customer_id = Orders.Customer_id<\/span>\n\n<span style=\"font-weight: 400;\">INNER JOIN<\/span><span style=\"font-weight: 400;\"> Products <\/span><span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> Orders.Product_id = Products.Product_id;<\/span><\/code><\/pre>\n\n\n\n<p><strong>B\u1ea3ng k\u1ebft qu\u1ea3:<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><b>Customer_id<\/b><\/td><td><b>Name<\/b><\/td><td><b>City<\/b><\/td><td><b>Order_id<\/b><\/td><td><b>Product_name<\/b><\/td><td><b>Price<\/b><\/td><td><b>Category<\/b><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">1<\/span><\/td><td><span style=\"font-weight: 400;\">Alice<\/span><\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">101<\/span><\/td><td><span style=\"font-weight: 400;\">Laptop<\/span><\/td><td><span style=\"font-weight: 400;\">1000<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Electronics<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">1<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Alice<\/span><\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">103<\/span><\/td><td><span style=\"font-weight: 400;\">Tablet<\/span><\/td><td><span style=\"font-weight: 400;\">500<\/span><\/td><td><span style=\"font-weight: 400;\">Electronics<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">2<\/span><\/td><td><span style=\"font-weight: 400;\">Bob<\/span><\/td><td><span style=\"font-weight: 400;\">Los Angeles<\/span><\/td><td><span style=\"font-weight: 400;\">102<\/span><\/td><td><span style=\"font-weight: 400;\">Smartphone<\/span><\/td><td><span style=\"font-weight: 400;\">800<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Electronics<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">3<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Charlie<\/span><\/td><td><span style=\"font-weight: 400;\">Chicago<\/span><\/td><td><span style=\"font-weight: 400;\">104<\/span><\/td><td><span style=\"font-weight: 400;\">Headphones<\/span><\/td><td><span style=\"font-weight: 400;\">200<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Accessories<\/span><\/p>\n<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-left-join\"><b>Left Join<\/b><\/h3>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1130\" height=\"640\" src=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-left-vippro.png\" alt=\"join trong sql - left join\" class=\"wp-image-74160\" srcset=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-left-vippro.png 1130w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-left-vippro-300x170.png 300w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-left-vippro-700x396.png 640w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-left-vippro-200x113.png 200w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-left-vippro-100x57.png 100w\" sizes=\"auto, (max-width: 1130px) 100vw, 1130px\" \/><\/figure>\n\n\n\n<p><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">LEFT JOIN (hay LEFT OUTER JOIN) l\u00e0 m\u1ed9t lo\u1ea1i JOIN trong SQL \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 k\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb hai b\u1ea3ng d\u1ef1a tr\u00ean m\u1ed9t \u0111i\u1ec1u ki\u1ec7n nh\u1ea5t \u0111\u1ecbnh. \u0110i\u1ec3m kh\u00e1c bi\u1ec7t c\u1ee7a LEFT JOIN so v\u1edbi INNER JOIN l\u00e0 n\u00f3 tr\u1ea3 v\u1ec1 t\u1ea5t c\u1ea3 c\u00e1c h\u00e0ng t\u1eeb b\u1ea3ng b\u00ean tr\u00e1i (b\u1ea3ng A), c\u00f9ng v\u1edbi c\u00e1c h\u00e0ng t\u01b0\u01a1ng \u1ee9ng t\u1eeb b\u1ea3ng b\u00ean ph\u1ea3i (b\u1ea3ng B). N\u1ebfu kh\u00f4ng c\u00f3 h\u00e0ng t\u01b0\u01a1ng \u1ee9ng trong b\u1ea3ng B, c\u00e1c c\u1ed9t t\u1eeb b\u1ea3ng B s\u1ebd ch\u1ee9a gi\u00e1 tr\u1ecb NULL.<\/span><\/p>\n\n\n\n<p><b>C\u00fa ph\u00e1p:<\/b><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> columns&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> left_table&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">LEFT<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> right_table&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> left_table.common_column = right_table.common_column;<\/span><\/code><\/pre>\n\n\n\n<p><b>V\u00ed d\u1ee5:<\/b><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">\u0110\u1ec3 l\u1ea5y th\u00f4ng tin c\u1ee7a t\u1ea5t c\u1ea3 kh\u00e1ch h\u00e0ng v\u00e0 \u0111\u01a1n h\u00e0ng c\u1ee7a h\u1ecd, b\u1ea5t k\u1ec3 kh\u00e1ch h\u00e0ng c\u00f3 \u0111\u01a1n h\u00e0ng hay kh\u00f4ng, ta th\u1ef1c hi\u1ec7n ph\u00e9p k\u1ebft n\u1ed1i LEFT JOIN nh\u01b0 sau:<\/span><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> Customers.Name, Customers.City, Orders.Order_id, Orders.Product_name, Orders.Price&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> Customers&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">LEFT<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> Orders&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> Customers.Customer_id = Orders.Customer_id;<\/span><\/code><\/pre>\n\n\n\n<p><b>B\u1ea3ng k\u1ebft qu\u1ea3:<\/b><span style=\"font-weight: 400;\"><br><\/span><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>\n<p style=\"text-align: left;\"><b>Name<\/b><\/p>\n<\/td><td><b>City<\/b><\/td><td><b>Order_id<\/b><\/td><td><b>Product_name<\/b><\/td><td><b>Price<\/b><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Alice<\/span><\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">101<\/span><\/td><td><span style=\"font-weight: 400;\">Laptop<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">1000<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Alice<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">103<\/span><\/td><td><span style=\"font-weight: 400;\">Tablet<\/span><\/td><td><span style=\"font-weight: 400;\">500<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Bob<\/span><\/td><td><span style=\"font-weight: 400;\">Los Angeles<\/span><\/td><td><span style=\"font-weight: 400;\">102<\/span><\/td><td><span style=\"font-weight: 400;\">Smartphone<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">800<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Charlie<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Chicago<\/span><\/td><td><span style=\"font-weight: 400;\">104<\/span><\/td><td><span style=\"font-weight: 400;\">Headphones<\/span><\/td><td><span style=\"font-weight: 400;\">200<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">David<\/span><\/td><td><span style=\"font-weight: 400;\">Miami<\/span><\/td><td><span style=\"font-weight: 400;\">NULL<\/span><\/td><td><span style=\"font-weight: 400;\">NULL<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">NULL<\/span><\/p>\n<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p><b>Gi\u1ea3i th\u00edch:<\/b><span style=\"font-weight: 400;\"> LEFT JOIN tr\u1ea3 v\u1ec1 t\u1ea5t c\u1ea3 c\u00e1c h\u00e0ng t\u1eeb b\u1ea3ng customers v\u00e0 c\u00e1c h\u00e0ng kh\u1edbp t\u1eeb b\u1ea3ng orders. N\u1ebfu kh\u00f4ng c\u00f3 s\u1ef1 kh\u1edbp, c\u00e1c c\u1ed9t t\u1eeb b\u1ea3ng orders s\u1ebd ch\u1ee9a gi\u00e1 tr\u1ecb NULL.<\/span><\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-right-join\"><b>Right Join<\/b><\/h3>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1098\" height=\"664\" src=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-right-vippro.png\" alt=\"join trong sql - right join\" class=\"wp-image-74159\" srcset=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-right-vippro.png 1098w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-right-vippro-300x181.png 300w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-right-vippro-700x423.png 640w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-right-vippro-200x121.png 200w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-right-vippro-100x60.png 100w\" sizes=\"auto, (max-width: 1098px) 100vw, 1098px\" \/><\/figure>\n\n\n\n<p><span style=\"font-weight: 400;\">RIGHT JOIN (hay RIGHT OUTER JOIN) l\u00e0 m\u1ed9t lo\u1ea1i JOIN trong SQL ho\u1ea1t \u0111\u1ed9ng ng\u01b0\u1ee3c l\u1ea1i so v\u1edbi LEFT JOIN. Khi s\u1eed d\u1ee5ng RIGHT JOIN, t\u1ea5t c\u1ea3 c\u00e1c h\u00e0ng t\u1eeb b\u1ea3ng b\u00ean ph\u1ea3i (b\u1ea3ng B) s\u1ebd \u0111\u01b0\u1ee3c tr\u1ea3 v\u1ec1, ngay c\u1ea3 khi kh\u00f4ng c\u00f3 h\u00e0ng t\u01b0\u01a1ng \u1ee9ng trong b\u1ea3ng b\u00ean tr\u00e1i (b\u1ea3ng A). N\u1ebfu kh\u00f4ng c\u00f3 h\u00e0ng t\u01b0\u01a1ng \u1ee9ng trong b\u1ea3ng A, c\u00e1c c\u1ed9t t\u1eeb b\u1ea3ng A trong k\u1ebft qu\u1ea3 s\u1ebd ch\u1ee9a gi\u00e1 tr\u1ecb NULL.<\/span><\/p>\n\n\n\n<p><b>C\u00fa ph\u00e1p:<\/b><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> columns&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> left_table&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">RIGHT<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> right_table&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> right_table.common_column = left_table.common_column;<\/span><\/code><\/pre>\n\n\n\n<p><b>V\u00ed d\u1ee5:&nbsp;<\/b><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> Customers.Name, Customers.City, Orders.Order_id, Orders.Product_Name, Orders.Price&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> Customers&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">RIGHT<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> Orders&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> Customers.Customer_id = Orders.Customer_id;<\/span><\/code><\/pre>\n\n\n\n<p><b>B\u1ea3ng k\u1ebft qu\u1ea3:<\/b><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>\n<p style=\"text-align: left;\"><b>Name<\/b><\/p>\n<\/td><td><b>City<\/b><\/td><td><b>Order_id<\/b><\/td><td><b>Product_name<\/b><\/td><td>\n<p style=\"text-align: left;\"><b>Price<\/b><\/p>\n<\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Alice<\/span><\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">101<\/span><\/td><td><span style=\"font-weight: 400;\">Laptop<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">1000<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Alice<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">103<\/span><\/td><td><span style=\"font-weight: 400;\">Tablet<\/span><\/td><td><span style=\"font-weight: 400;\">500<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Bob<\/span><\/td><td><span style=\"font-weight: 400;\">Los Angeles<\/span><\/td><td><span style=\"font-weight: 400;\">102<\/span><\/td><td><span style=\"font-weight: 400;\">Smartphone<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">800<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Charlie<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Chicago<\/span><\/td><td><span style=\"font-weight: 400;\">104<\/span><\/td><td><span style=\"font-weight: 400;\">Headphones<\/span><\/td><td><span style=\"font-weight: 400;\">200<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">NULL<\/span><\/td><td><span style=\"font-weight: 400;\">NULL<\/span><\/td><td><span style=\"font-weight: 400;\">105<\/span><\/td><td><span style=\"font-weight: 400;\">Monitor<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">300<\/span><\/p>\n<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p><b>Gi\u1ea3i th\u00edch:<\/b><span style=\"font-weight: 400;\"> RIGHT JOIN tr\u1ea3 v\u1ec1 t\u1ea5t c\u1ea3 c\u00e1c h\u00e0ng t\u1eeb b\u1ea3ng orders v\u00e0 c\u00e1c h\u00e0ng kh\u1edbp t\u1eeb b\u1ea3ng customers. N\u1ebfu kh\u00f4ng c\u00f3 s\u1ef1 kh\u1edbp, c\u00e1c c\u1ed9t t\u1eeb b\u1ea3ng customers s\u1ebd ch\u1ee9a gi\u00e1 tr\u1ecb NULL.<\/span><\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-full-join\"><b>Full Join<\/b><\/h3>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"682\" height=\"472\" src=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-full-vippro.png\" alt=\"join trong sql - full join\" class=\"wp-image-74158\" srcset=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-full-vippro.png 682w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-full-vippro-300x208.png 300w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-full-vippro-650x450.png 640w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-full-vippro-200x138.png 200w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-full-vippro-100x69.png 100w\" sizes=\"auto, (max-width: 682px) 100vw, 682px\" \/><\/figure>\n\n\n\n<p><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">FULL JOIN (hay FULL OUTER JOIN) l\u00e0 m\u1ed9t lo\u1ea1i JOIN k\u1ebft h\u1ee3p c\u1ea3 k\u1ebft qu\u1ea3 c\u1ee7a LEFT OUTER JOIN v\u00e0 RIGHT OUTER JOIN. FULL JOIN tr\u1ea3 v\u1ec1 t\u1ea5t c\u1ea3 c\u00e1c h\u00e0ng t\u1eeb c\u1ea3 hai b\u1ea3ng, v\u00e0 \u0111i\u1ec1n c\u00e1c gi\u00e1 tr\u1ecb NULL cho c\u00e1c h\u00e0ng kh\u00f4ng c\u00f3 t\u01b0\u01a1ng \u1ee9ng trong b\u1ea3ng kia. \u0110i\u1ec1u n\u00e0y c\u00f3 ngh\u0129a l\u00e0 FULL JOIN c\u00f3 th\u1ec3 ph\u00e1t hi\u1ec7n v\u00e0 tr\u1ea3 v\u1ec1 c\u00e1c h\u00e0ng m\u00e0 kh\u00f4ng c\u00f3 k\u1ebft qu\u1ea3 kh\u1edbp trong b\u1ea3ng \u0111\u01b0\u1ee3c k\u1ebft h\u1ee3p.<\/span><\/p>\n\n\n\n<p><b>C\u00fa ph\u00e1p:<\/b><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> columns&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> table1&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FULL<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> table2&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> table1.common_column = table2.common_column;<\/span><\/code><\/pre>\n\n\n\n<p><b>V\u00ed d\u1ee5:<\/b><span style=\"font-weight: 400;\"> \u0110\u1ec3 l\u1ea5y th\u00f4ng tin t\u1ea5t c\u1ea3 kh\u00e1ch h\u00e0ng v\u00e0 \u0111\u01a1n h\u00e0ng, bao g\u1ed3m c\u1ea3 nh\u1eefng kh\u00e1ch h\u00e0ng kh\u00f4ng c\u00f3 \u0111\u01a1n h\u00e0ng v\u00e0 \u0111\u01a1n h\u00e0ng kh\u00f4ng c\u00f3 kh\u00e1ch h\u00e0ng, ta d\u00f9ng ph\u00e9p k\u1ebft FULL JOIN nh\u01b0 sau:<\/span><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> Customers.Name, Customers.City, Orders.Order_id, Orders.Product_name, Orders.Price&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> Customers&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FULL<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> Orders&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> Customers.Customer_id = Orders.Customer_id;<\/span><\/code><\/pre>\n\n\n\n<p><b>B\u1ea3ng k\u1ebft qu\u1ea3:<\/b><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>\n<p style=\"text-align: left;\"><b>Name<\/b><\/p>\n<\/td><td><b>City<\/b><\/td><td><b>Order_id<\/b><\/td><td><b>Product_name<\/b><\/td><td>\n<p style=\"text-align: left;\"><b>Price<\/b><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Alice<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">101<\/span><\/td><td><span style=\"font-weight: 400;\">Laptop<\/span><\/td><td><span style=\"font-weight: 400;\">1000<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Alice<\/span><\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">103<\/span><\/td><td><span style=\"font-weight: 400;\">Tablet<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">500<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Bob<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Los Angeles<\/span><\/td><td><span style=\"font-weight: 400;\">102<\/span><\/td><td><span style=\"font-weight: 400;\">Smartphone<\/span><\/td><td><span style=\"font-weight: 400;\">800<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Charlie<\/span><\/td><td><span style=\"font-weight: 400;\">Chicago<\/span><\/td><td><span style=\"font-weight: 400;\">104<\/span><\/td><td><span style=\"font-weight: 400;\">Headphones<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">200<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">David<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Miami<\/span><\/td><td><span style=\"font-weight: 400;\">NULL<\/span><\/td><td><span style=\"font-weight: 400;\">NULL<\/span><\/td><td><span style=\"font-weight: 400;\">NULL<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">NULL<\/span><\/td><td><span style=\"font-weight: 400;\">NULL<\/span><\/td><td><span style=\"font-weight: 400;\">105<\/span><\/td><td><span style=\"font-weight: 400;\">Monitor<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">300<\/span><\/p>\n<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p><b>Gi\u1ea3i th\u00edch:<\/b><span style=\"font-weight: 400;\"> FULL JOIN tr\u1ea3 v\u1ec1 t\u1ea5t c\u1ea3 c\u00e1c b\u1ea3n ghi khi th\u1ecfa m\u00e3n \u0111i\u1ec1u ki\u1ec7n \u1edf m\u1ed9t trong hai b\u1ea3ng. C\u00e1c b\u1ea3n ghi kh\u00f4ng kh\u1edbp v\u1edbi \u0111i\u1ec1u ki\u1ec7n trong b\u1ea3ng c\u00f2n l\u1ea1i s\u1ebd ch\u1ee9a gi\u00e1 tr\u1ecb NULL.<\/span><\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-cross-join\"><b>Cross Join<\/b><\/h3>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1600\" height=\"635\" src=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-cross-vippro.jpg\" alt=\"join trong sql - cross join\" class=\"wp-image-74157\" srcset=\"https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-cross-vippro.jpg 1600w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-cross-vippro-300x119.jpg 300w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-cross-vippro-700x278.jpg 640w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-cross-vippro-200x79.jpg 200w, https:\/\/itviec.com\/blog\/wp-content\/uploads\/2024\/06\/join-cross-vippro-100x40.jpg 100w\" sizes=\"auto, (max-width: 1600px) 100vw, 1600px\" \/><\/figure>\n\n\n\n<p><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">CROSS JOIN l\u00e0 d\u1ea1ng JOIN \u0111\u01a1n gi\u1ea3n nh\u1ea5t trong SQL. N\u00f3 k\u1ebft h\u1ee3p m\u1ed7i h\u00e0ng t\u1eeb m\u1ed9t b\u1ea3ng v\u1edbi t\u1ea5t c\u1ea3 c\u00e1c h\u00e0ng t\u1eeb b\u1ea3ng kh\u00e1c. N\u00f3i c\u00e1ch kh\u00e1c, CROSS JOIN t\u1ea1o ra s\u1ef1 k\u1ebft h\u1ee3p c\u1ee7a m\u1ed7i h\u00e0ng t\u1eeb b\u1ea3ng \u0111\u1ea7u ti\u00ean v\u1edbi t\u1ea5t c\u1ea3 c\u00e1c h\u00e0ng trong b\u1ea3ng th\u1ee9 hai.<\/span><\/p>\n\n\n\n<p><b>C\u00fa ph\u00e1p:<\/b><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> columns&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> table1&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">CROSS<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> table2;<\/span><\/code><\/pre>\n\n\n\n<p><b>V\u00ed d\u1ee5: <\/b><span style=\"font-weight: 400;\">\u0110\u1ec3 l\u1ea5y t\u1ea5t c\u1ea3 c\u00e1c k\u1ebft h\u1ee3p c\u00f3 th\u1ec3 c\u1ee7a kh\u00e1ch h\u00e0ng v\u00e0 \u0111\u01a1n h\u00e0ng, ta d\u00f9ng ph\u00e9p k\u1ebft CROSS JOIN nh\u01b0 sau<\/span><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> Customers.Name, Customers.City, Orders.Order_id, Orders.Product_name, Orders.Price&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> Customers&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">CROSS<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> Orders;<\/span><\/code><\/pre>\n\n\n\n<p><b>B\u1ea3ng k\u1ebft qu\u1ea3:<\/b><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>\n<p style=\"text-align: left;\"><b>Name<\/b><\/p>\n<\/td><td><b>City<\/b><\/td><td><b>Order_id<\/b><\/td><td><b>Product_name<\/b><\/td><td>\n<p style=\"text-align: left;\"><b>Price<\/b><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Alice<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">101<\/span><\/td><td><span style=\"font-weight: 400;\">Laptop<\/span><\/td><td><span style=\"font-weight: 400;\">1000<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Alice<\/span><\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">102<\/span><\/td><td><span style=\"font-weight: 400;\">Smartphone<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">800<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Alice<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">103<\/span><\/td><td><span style=\"font-weight: 400;\">Tablet<\/span><\/td><td><span style=\"font-weight: 400;\">500<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Alice<\/span><\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">104<\/span><\/td><td><span style=\"font-weight: 400;\">Headphones<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">200<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Alice<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">New York<\/span><\/td><td><span style=\"font-weight: 400;\">105<\/span><\/td><td><span style=\"font-weight: 400;\">Monitor<\/span><\/td><td><span style=\"font-weight: 400;\">300<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Bob<\/span><\/td><td><span style=\"font-weight: 400;\">Los Angeles<\/span><\/td><td><span style=\"font-weight: 400;\">101<\/span><\/td><td><span style=\"font-weight: 400;\">Laptop<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">1000<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Bob<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Los Angeles<\/span><\/td><td><span style=\"font-weight: 400;\">102<\/span><\/td><td><span style=\"font-weight: 400;\">Smartphone<\/span><\/td><td><span style=\"font-weight: 400;\">800<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Bob<\/span><\/td><td><span style=\"font-weight: 400;\">Los Angeles<\/span><\/td><td><span style=\"font-weight: 400;\">103<\/span><\/td><td><span style=\"font-weight: 400;\">Tablet<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">500<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Bob<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Los Angeles<\/span><\/td><td><span style=\"font-weight: 400;\">104<\/span><\/td><td><span style=\"font-weight: 400;\">Headphones<\/span><\/td><td><span style=\"font-weight: 400;\">200<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Bob<\/span><\/td><td><span style=\"font-weight: 400;\">Los Angeles<\/span><\/td><td><span style=\"font-weight: 400;\">105<\/span><\/td><td><span style=\"font-weight: 400;\">Monitor<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">300<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Charlie<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Chicago<\/span><\/td><td><span style=\"font-weight: 400;\">101<\/span><\/td><td><span style=\"font-weight: 400;\">Laptop<\/span><\/td><td><span style=\"font-weight: 400;\">1000<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Charlie<\/span><\/td><td><span style=\"font-weight: 400;\">Chicago<\/span><\/td><td><span style=\"font-weight: 400;\">102<\/span><\/td><td><span style=\"font-weight: 400;\">Smartphone<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">800<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Charlie<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Chicago<\/span><\/td><td><span style=\"font-weight: 400;\">103<\/span><\/td><td><span style=\"font-weight: 400;\">Tablet<\/span><\/td><td><span style=\"font-weight: 400;\">500<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">Charlie<\/span><\/td><td><span style=\"font-weight: 400;\">Chicago<\/span><\/td><td><span style=\"font-weight: 400;\">104<\/span><\/td><td><span style=\"font-weight: 400;\">Headphones<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">200<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Charlie<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Chicago<\/span><\/td><td><span style=\"font-weight: 400;\">105<\/span><\/td><td><span style=\"font-weight: 400;\">Monitor<\/span><\/td><td><span style=\"font-weight: 400;\">300<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">David<\/span><\/td><td><span style=\"font-weight: 400;\">Miami<\/span><\/td><td><span style=\"font-weight: 400;\">101<\/span><\/td><td><span style=\"font-weight: 400;\">Laptop<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">1000<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">David<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Miami<\/span><\/td><td><span style=\"font-weight: 400;\">102<\/span><\/td><td><span style=\"font-weight: 400;\">Smartphone<\/span><\/td><td><span style=\"font-weight: 400;\">800<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">David<\/span><\/td><td><span style=\"font-weight: 400;\">Miami<\/span><\/td><td><span style=\"font-weight: 400;\">103<\/span><\/td><td><span style=\"font-weight: 400;\">Tablet<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">500<\/span><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">David<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Miami<\/span><\/td><td><span style=\"font-weight: 400;\">104<\/span><\/td><td><span style=\"font-weight: 400;\">Headphones<\/span><\/td><td><span style=\"font-weight: 400;\">200<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">David<\/span><\/td><td><span style=\"font-weight: 400;\">Miami<\/span><\/td><td><span style=\"font-weight: 400;\">105<\/span><\/td><td><span style=\"font-weight: 400;\">Monitor<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">300<\/span><\/p>\n<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p><b>Gi\u1ea3i th\u00edch:<\/b><span style=\"font-weight: 400;\"> CROSS JOIN tr\u1ea3 v\u1ec1 t\u1ea5t c\u1ea3 c\u00e1c k\u1ebft h\u1ee3p c\u00f3 th\u1ec3 gi\u1eefa c\u00e1c h\u00e0ng trong b\u1ea3ng customers v\u00e0 orders, t\u1ea1o th\u00e0nh s\u1ea3n ph\u1ea9m Cartesian c\u1ee7a hai b\u1ea3ng. M\u1ed7i h\u00e0ng c\u1ee7a b\u1ea3ng customers \u0111\u01b0\u1ee3c k\u1ebft h\u1ee3p v\u1edbi m\u1ed7i h\u00e0ng c\u1ee7a b\u1ea3ng orders.<\/span><\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-natural-join\"><b>Natural JOIN<\/b><\/h3>\n\n\n\n<p><span style=\"font-weight: 400;\">Natural join l\u00e0 m\u1ed9t lo\u1ea1i JOIN trong SQL s\u1eed d\u1ee5ng \u0111\u1ec3 k\u1ebft h\u1ee3p c\u00e1c b\u1ea3ng d\u1ef1a tr\u00ean c\u00e1c c\u1ed9t chung c\u00f3 c\u00f9ng t\u00ean v\u00e0 ki\u1ec3u d\u1eef li\u1ec7u trong c\u1ea3 hai b\u1ea3ng. NATURAL JOIN t\u1ef1 \u0111\u1ed9ng ph\u00e1t hi\u1ec7n v\u00e0 s\u1eed d\u1ee5ng c\u00e1c c\u1ed9t chung n\u00e0y \u0111\u1ec3 th\u1ef1c hi\u1ec7n ph\u00e9p k\u1ebft h\u1ee3p m\u00e0 kh\u00f4ng c\u1ea7n ch\u1ec9 \u0111\u1ecbnh r\u00f5 r\u00e0ng \u0111i\u1ec1u ki\u1ec7n k\u1ebft h\u1ee3p.<\/span><\/p>\n\n\n\n<p><b>C\u00fa ph\u00e1p:<\/b><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\"><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> *&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> TableA&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">NATURAL<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> TableB;<\/span><\/pre>\n\n\n\n<p><span style=\"font-weight: 400;\">\u0110i\u1ec3m \u0111\u1eb7c bi\u1ec7t c\u1ee7a NATURAL JOIN l\u00e0:<\/span><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><span style=\"font-weight: 400;\">Hai b\u1ea3ng ph\u1ea3i c\u00f3 \u00edt nh\u1ea5t m\u1ed9t c\u1ed9t chung v\u1edbi c\u00f9ng t\u00ean v\u00e0 ki\u1ec3u d\u1eef li\u1ec7u.<\/span><\/li>\n\n\n\n<li><span style=\"font-weight: 400;\">K\u1ebft qu\u1ea3 c\u1ee7a ph\u00e9p k\u1ebft h\u1ee3p ch\u1ec9 bao g\u1ed3m c\u00e1c h\u00e0ng m\u00e0 gi\u00e1 tr\u1ecb trong c\u00e1c c\u1ed9t chung \u0111\u00f3 kh\u1edbp nhau.<\/span><\/li>\n<\/ul>\n\n\n\n<p><span style=\"font-weight: 400;\">Qu\u00e1 tr\u00ecnh th\u1ef1c hi\u1ec7n Natural join c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c hi\u1ec3u nh\u01b0 sau:<\/span><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><span style=\"font-weight: 400;\">Natural JOIN c\u00f3 th\u1ec3 t\u1ea1o t\u00edch Descartes c\u1ee7a hai b\u1ea3ng (gi\u1ed1ng nh\u01b0 CROSS JOIN), nh\u01b0ng t\u00f9y v\u00e0o tr\u01b0\u1eddng h\u1ee3p m\u00e0 n\u00f3 s\u1ebd t\u1ea1o t\u00edch to\u00e0n ph\u1ea7n ho\u1eb7c 1 ph\u1ea7n<\/span><\/li>\n\n\n\n<li><span style=\"font-weight: 400;\">L\u1ecdc c\u00e1c h\u00e0ng trong k\u1ebft qu\u1ea3 t\u00edch Descartes n\u00e0y sao cho c\u00e1c gi\u00e1 tr\u1ecb trong c\u00e1c c\u1ed9t chung kh\u1edbp nhau.<\/span><\/li>\n\n\n\n<li><span style=\"font-weight: 400;\">Ch\u1ec9 gi\u1eef l\u1ea1i c\u00e1c h\u00e0ng c\u00f3 gi\u00e1 tr\u1ecb kh\u1edbp v\u00e0 lo\u1ea1i b\u1ecf c\u00e1c c\u1ed9t tr\u00f9ng l\u1eb7p.<\/span><\/li>\n<\/ul>\n\n\n\n<p><b>V\u00ed d\u1ee5:<\/b><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">Gi\u1ea3 s\u1eed ta c\u00f3 2 b\u1ea3ng sau:<\/span><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><span style=\"font-weight: 400;\">Table A:<\/span><\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><b>ID<\/b><\/td><td><b>Name<\/b><\/td><td>\n<p style=\"text-align: left;\"><b>City<\/b><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">1<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">Alice<\/span><\/td><td><span style=\"font-weight: 400;\">Ha Noi<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">2<\/span><\/td><td><span style=\"font-weight: 400;\">Bob<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Ho Chi Minh<\/span><\/p>\n<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<ul class=\"wp-block-list\">\n<li><span style=\"font-weight: 400;\">Table B:<\/span><\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>\n<p style=\"text-align: left;\"><b>ID<\/b><\/p>\n<\/td><td><b>Age<\/b><\/td><td><b>City<\/b><\/td><td>\n<p style=\"text-align: left;\"><b>Email<\/b><\/p>\n<\/td><\/tr><tr><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">1<\/span><\/p>\n<\/td><td><span style=\"font-weight: 400;\">25<\/span><\/td><td><span style=\"font-weight: 400;\">Ha Noi<\/span><\/td><td><span style=\"font-weight: 400;\">alice@gmail.com<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">3<\/span><\/td><td><span style=\"font-weight: 400;\">30<\/span><\/td><td><span style=\"font-weight: 400;\">Vung Tau<\/span><\/td><td>\n<p style=\"text-align: left;\"><span style=\"font-weight: 400;\">brian@gmail.com<\/span><\/p>\n<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<ul class=\"wp-block-list\">\n<li><span style=\"font-weight: 400;\">Ph\u00e9p k\u1ebft h\u1ee3p Natural join gi\u1eefa TableA v\u00e0 TableB:<\/span><\/li>\n<\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">SELECT<\/span><span style=\"font-weight: 400;\"> *&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> TableA&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">NATURAL<\/span> <span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> TableB;<\/span><\/code><\/pre>\n\n\n\n<ul class=\"wp-block-list\">\n<li><span style=\"font-weight: 400;\">K\u1ebft qu\u1ea3 s\u1ebd \u0111\u01b0\u1ee3c:<\/span><\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>\n<p style=\"text-align: center;\"><b>ID<\/b><\/p>\n<\/td><td><b>Name<\/b><\/td><td><b>City<\/b><\/td><td><b>Age<\/b><\/td><td><b>Email<\/b><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">1<\/span><\/td><td><span style=\"font-weight: 400;\">Alice<\/span><\/td><td><span style=\"font-weight: 400;\">Ha Noi<\/span><\/td><td><span style=\"font-weight: 400;\">25<\/span><\/td><td><span style=\"font-weight: 400;\">alice@gmail.com<\/span><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p><b>Gi\u1ea3i th\u00edch: <\/b><span style=\"font-weight: 400;\">m\u1eb7c d\u00f9 \u1edf c\u1ea3 2 b\u1ea3ng \u0111\u1ec1u c\u00f3 c\u1ed9t Id v\u00e0 c\u1ed9t City nh\u01b0ng NATURAL JOIN ch\u1ec9 gi\u1eef l\u1ea1i c\u00e1c h\u00e0ng kh\u1edbp gi\u00e1 tr\u1ecb v\u00e0 lo\u1ea1i b\u1ecf c\u00e1c c\u1ed9t tr\u00f9ng l\u1eb7p n\u00ean c\u1ed9t Id v\u00e0 c\u1ed9t City ch\u1ec9 xu\u1ea5t hi\u1ec7n m\u1ed9t l\u1ea7n trong b\u1ea3ng k\u1ebft qu\u1ea3.<\/span><\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>\u1ee8ng tuy\u1ec3n <a href=\"https:\/\/itviec.com\/viec-lam-it\/sql?utm_medium=anchor_text_mid&amp;utm_source=blog&amp;utm_campaign=viec_lam_sql&amp;utm_content=join_trong_sql\" target=\"_blank\" rel=\"noreferrer noopener\">vi\u1ec7c l\u00e0m SQL<\/a> ngay tr\u00ean ITviec<\/strong><\/p>\n<\/blockquote>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-delete-join-la-gi\"><span class=\"ez-toc-section\" id=\"DELETE_JOIN_la_gi\"><\/span><b>DELETE JOIN l\u00e0 g\u00ec?<\/b><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p><span style=\"font-weight: 400;\">DELETE JOIN trong SQL l\u00e0 m\u1ed9t thao t\u00e1c cho ph\u00e9p x\u00f3a c\u00e1c h\u00e0ng trong m\u1ed9t b\u1ea3ng d\u1ef1a tr\u00ean c\u00e1c \u0111i\u1ec1u ki\u1ec7n li\u00ean quan \u0111\u1ebfn m\u1ed9t b\u1ea3ng kh\u00e1c. B\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng c\u00e2u l\u1ec7nh DELETE k\u1ebft h\u1ee3p v\u1edbi JOIN, c\u00f3 th\u1ec3 x\u00f3a c\u00e1c h\u00e0ng m\u00e0 th\u1ecfa m\u00e3n c\u00e1c \u0111i\u1ec1u ki\u1ec7n \u0111\u01b0\u1ee3c \u0111\u1ecbnh ngh\u0129a th\u00f4ng qua ph\u00e9p k\u1ebft h\u1ee3p (join) gi\u1eefa c\u00e1c b\u1ea3ng.<\/span><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">Tuy nhi\u00ean, c\u1ea7n l\u01b0u \u00fd r\u1eb1ng c\u00fa ph\u00e1p DELETE JOIN kh\u00f4ng ph\u1ea3i l\u00e0 ti\u00eau chu\u1ea9n SQL v\u00e0 c\u00f3 th\u1ec3 kh\u00f4ng \u0111\u01b0\u1ee3c h\u1ed7 tr\u1ee3 \u1edf m\u1ed9t s\u1ed1 h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u (DBMS). Ngo\u00e0i ra, c\u00fa ph\u00e1p DELETE JOIN s\u1ebd ph\u1ee5 thu\u1ed9c v\u00e0o c\u00fa ph\u00e1p c\u1ee5 th\u1ec3 c\u1ee7a h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u \u0111ang \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng. V\u00ed d\u1ee5, c\u00fa ph\u00e1p DELETE JOIN trong MySQL c\u00f3 th\u1ec3 kh\u00e1c v\u1edbi trong SQL Server ho\u1eb7c PostgreSQL.<\/span><\/p>\n\n\n\n<p><b>C\u00fa ph\u00e1p:<\/b><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">DELETE<\/span><span style=\"font-weight: 400;\"> table1&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> table1&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> table2&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> table1.attribute_name = table2.attribute_name&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">WHERE<\/span> <span style=\"font-weight: 400;\">condition<\/span><span style=\"font-weight: 400;\">;<\/span><\/code><\/pre>\n\n\n\n<p><b>V\u00ed d\u1ee5:&nbsp;<\/b><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">Gi\u1ea3 s\u1eed ta c\u00f3 2 b\u1ea3ng Order v\u00e0 Customer nh\u01b0 sau:<\/span><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><span style=\"font-weight: 400;\">B\u1ea3ng Order:<\/span><\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><p style=\"text-align: left;\"><b>OrderID<\/b><\/p><\/td><td><b>CustomerID<\/b><\/td><td><b>OrderDate<\/b><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">1<\/span><\/td><td><span style=\"font-weight: 400;\">1<\/span><\/td><td><p style=\"text-align: left;\"><span style=\"font-weight: 400;\">2023-01-01<\/span><\/p><\/td><\/tr><tr><td><p style=\"text-align: left;\"><span style=\"font-weight: 400;\">2<\/span><\/p><\/td><td><span style=\"font-weight: 400;\">2<\/span><\/td><td><span style=\"font-weight: 400;\">2023-01-02<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">3<\/span><\/td><td><span style=\"font-weight: 400;\">3<\/span><\/td><td><p style=\"text-align: left;\"><span style=\"font-weight: 400;\">2023-01-03<\/span><\/p><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<ul class=\"wp-block-list\">\n<li><span style=\"font-weight: 400;\">B\u1ea3ng Customer:<\/span><\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><p style=\"text-align: left;\"><b>CustomerID<\/b><\/p><\/td><td><b>CustomerName<\/b><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">1<\/span><\/td><td><p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Alice<\/span><\/p><\/td><\/tr><tr><td><p style=\"text-align: left;\"><span style=\"font-weight: 400;\">2<\/span><\/p><\/td><td><span style=\"font-weight: 400;\">Bob<\/span><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">3<\/span><\/td><td><p style=\"text-align: left;\"><span style=\"font-weight: 400;\">Charlie<\/span><\/p><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p><span style=\"font-weight: 400;\">\u0110\u1ec3 x\u00f3a c\u00e1c \u0111\u01a1n h\u00e0ng t\u1eeb b\u1ea3ng Orders c\u1ee7a kh\u00e1ch h\u00e0ng c\u00f3 t\u00ean l\u00e0 &#8220;Bob&#8221;. C\u00e2u l\u1ec7nh DELETE JOIN s\u1ebd nh\u01b0 sau:<\/span><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code><span style=\"font-weight: 400;\">DELETE<\/span><span style=\"font-weight: 400;\"> O&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">FROM<\/span><span style=\"font-weight: 400;\"> Orders O&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">JOIN<\/span><span style=\"font-weight: 400;\"> Customers C&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">ON<\/span><span style=\"font-weight: 400;\"> O.CustomerID = C.CustomerID&nbsp;<\/span>\n\n<span style=\"font-weight: 400;\">WHERE<\/span><span style=\"font-weight: 400;\"> C.CustomerName = <\/span><span style=\"font-weight: 400;\">'Bob'<\/span><span style=\"font-weight: 400;\">;<\/span><\/code><\/pre>\n\n\n\n<p><span style=\"font-weight: 400;\">Sau khi th\u1ef1c hi\u1ec7n c\u00fa ph\u00e1p tr\u00ean th\u00ec b\u1ea3ng Order s\u1ebd nh\u01b0 sau:<\/span><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><p style=\"text-align: left;\"><b>OrderID<\/b><\/p><\/td><td><b>CustomerID<\/b><\/td><td><b>OrderDate<\/b><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">1<\/span><\/td><td><span style=\"font-weight: 400;\">1<\/span><\/td><td><p style=\"text-align: left;\"><span style=\"font-weight: 400;\">2023-01-01<\/span><\/p><\/td><\/tr><tr><td><span style=\"font-weight: 400;\">3<\/span><\/td><td><span style=\"font-weight: 400;\">3<\/span><\/td><td><p style=\"text-align: left;\"><span style=\"font-weight: 400;\">2023-01-03<\/span><\/p><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p><b>Gi\u1ea3i th\u00edch: <\/b><span style=\"font-weight: 400;\">T\u1ea5t c\u1ea3 c\u00e1c h\u00e0ng trong b\u1ea3ng Orders m\u00e0 CustomerID t\u01b0\u01a1ng \u1ee9ng v\u1edbi kh\u00e1ch h\u00e0ng c\u00f3 t\u00ean l\u00e0 &#8220;Bob&#8221; s\u1ebd b\u1ecb x\u00f3a. Trong b\u1ea3ng Customers, CustomerID c\u1ee7a Bob l\u00e0 2 n\u00ean h\u00e0ng trong Orders c\u00f3 CustomerID l\u00e0 2 s\u1ebd b\u1ecb x\u00f3a. C\u00f2n b\u1ea3ng Customers v\u1eabn gi\u1eef nguy\u00ean v\u00ec ch\u00fang ta ch\u1ec9 x\u00f3a c\u00e1c h\u00e0ng trong b\u1ea3ng Orders.<\/span><\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-cau-h\u1ecfi-th\u01b0\u1eddng-g\u1eb7p-v\u1ec1-cach-s\u1eed-d\u1ee5ng-join-trong-sql\"><span class=\"ez-toc-section\" id=\"Cau_hoi_thuong_gap_ve_cach_su_dung_JOIN_trong_SQL\"><\/span><b>C\u00e2u h\u1ecfi th\u01b0\u1eddng g\u1eb7p v\u1ec1 c\u00e1ch s\u1eed d\u1ee5ng JOIN trong SQL<\/b><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-self-join-la-gi\"><b>SELF JOIN l\u00e0 g\u00ec?<\/b><\/h3>\n\n\n\n<p><span style=\"font-weight: 400;\">SELF JOIN l\u00e0 m\u1ed9t tr\u01b0\u1eddng h\u1ee3p \u0111\u1eb7c bi\u1ec7t c\u1ee7a JOIN trong SQL, trong \u0111\u00f3 m\u1ed9t b\u1ea3ng \u0111\u01b0\u1ee3c k\u1ebft h\u1ee3p v\u1edbi ch\u00ednh n\u00f3. Thao t\u00e1c n\u00e0y h\u1eefu \u00edch khi b\u1ea1n c\u1ea7n so s\u00e1nh c\u00e1c h\u00e0ng trong c\u00f9ng m\u1ed9t b\u1ea3ng ho\u1eb7c khi b\u1ea1n c\u1ea7n truy xu\u1ea5t d\u1eef li\u1ec7u theo m\u1ed1i quan h\u1ec7 gi\u1eefa c\u00e1c h\u00e0ng trong c\u00f9ng m\u1ed9t b\u1ea3ng.<\/span><\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-sql-server-s\u1eed-d\u1ee5ng-nh\u1eefng-lo\u1ea1i-phep-n\u1ed1i-v\u1eadt-ly-nao-d\u1ec3-th\u1ef1c-hi\u1ec7n-cac-phep-n\u1ed1i-logic\"><b>SQL Server s\u1eed d\u1ee5ng nh\u1eefng lo\u1ea1i ph\u00e9p n\u1ed1i v\u1eadt l\u00fd n\u00e0o \u0111\u1ec3 th\u1ef1c hi\u1ec7n c\u00e1c ph\u00e9p n\u1ed1i logic?<\/b><\/h3>\n\n\n\n<p><span style=\"font-weight: 400;\">SQL Server s\u1eed d\u1ee5ng b\u1ed1n lo\u1ea1i ph\u00e9p n\u1ed1i v\u1eadt l\u00fd \u0111\u1ec3 th\u1ef1c hi\u1ec7n c\u00e1c ph\u00e9p n\u1ed1i logic:<\/span><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><span style=\"font-weight: 400;\">Nested Loops joins (Ph\u00e9p n\u1ed1i v\u00f2ng l\u1eb7p l\u1ed3ng nhau): L\u00e0 ph\u01b0\u01a1ng ph\u00e1p n\u1ed1i \u0111\u01a1n gi\u1ea3n nh\u1ea5t. V\u1edbi Nested Loops joins, SQL Server l\u1eb7p qua t\u1eebng h\u00e0ng c\u1ee7a b\u1ea3ng ngo\u00e0i v\u00e0 v\u1edbi m\u1ed7i h\u00e0ng, n\u00f3 t\u00ecm ki\u1ebfm c\u00e1c h\u00e0ng kh\u1edbp trong b\u1ea3ng trong. Ph\u00e9p n\u1ed1i n\u00e0y th\u01b0\u1eddng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng khi m\u1ed9t trong hai b\u1ea3ng nh\u1ecf ho\u1eb7c khi ch\u1ec9 c\u00f3 m\u1ed9t s\u1ed1 l\u01b0\u1ee3ng nh\u1ecf c\u00e1c h\u00e0ng ph\u00f9 h\u1ee3p t\u1eeb b\u1ea3ng ngo\u00e0i.<\/span><\/li>\n\n\n\n<li><span style=\"font-weight: 400;\">Merge joins (Ph\u00e9p n\u1ed1i h\u1ee3p nh\u1ea5t): Y\u00eau c\u1ea7u c\u1ea3 hai b\u1ea3ng \u0111\u1ea7u v\u00e0o ph\u1ea3i \u0111\u01b0\u1ee3c s\u1eafp x\u1ebfp tr\u01b0\u1edbc theo c\u1ed9t n\u1ed1i. Khi c\u00e1c b\u1ea3ng \u0111\u00e3 \u0111\u01b0\u1ee3c s\u1eafp x\u1ebfp, SQL Server c\u00f3 th\u1ec3 h\u1ee3p nh\u1ea5t hai b\u1ea3ng b\u1eb1ng c\u00e1ch qu\u00e9t c\u1ea3 hai b\u1ea3ng m\u1ed9t c\u00e1ch tu\u1ea7n t\u1ef1 v\u00e0 k\u1ebft h\u1ee3p c\u00e1c h\u00e0ng kh\u1edbp. Ph\u00e9p n\u1ed1i n\u00e0y th\u01b0\u1eddng hi\u1ec7u qu\u1ea3 khi c\u1ea3 hai b\u1ea3ng \u0111\u1ea7u v\u00e0o \u0111\u00e3 \u0111\u01b0\u1ee3c s\u1eafp x\u1ebfp theo th\u1ee9 t\u1ef1 ho\u1eb7c khi c\u00e1c b\u1ea3ng \u0111\u01b0\u1ee3c s\u1eafp x\u1ebfp b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng c\u00e1c ch\u1ec9 m\u1ee5c.<\/span><\/li>\n\n\n\n<li><span style=\"font-weight: 400;\">Hash joins (Ph\u00e9p n\u1ed1i b\u0103m): S\u1eed d\u1ee5ng m\u1ed9t b\u1ea3ng b\u0103m \u0111\u1ec3 n\u1ed1i c\u00e1c h\u00e0ng. \u0110\u1ea7u ti\u00ean, SQL Server x\u00e2y d\u1ef1ng m\u1ed9t b\u1ea3ng b\u0103m t\u1eeb b\u1ea3ng \u0111\u1ea7u v\u00e0o nh\u1ecf h\u01a1n, v\u00e0 sau \u0111\u00f3 n\u00f3 qu\u00e9t b\u1ea3ng \u0111\u1ea7u v\u00e0o l\u1edbn h\u01a1n v\u00e0 d\u00f2 t\u00ecm c\u00e1c h\u00e0ng kh\u1edbp trong b\u1ea3ng b\u0103m. Ph\u00e9p n\u1ed1i n\u00e0y th\u01b0\u1eddng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng khi c\u00e1c b\u1ea3ng \u0111\u1ea7u v\u00e0o kh\u00f4ng \u0111\u01b0\u1ee3c s\u1eafp x\u1ebfp v\u00e0 kh\u00f4ng c\u00f3 ch\u1ec9 m\u1ee5c tr\u00ean c\u00e1c c\u1ed9t n\u1ed1i.<\/span><\/li>\n\n\n\n<li><span style=\"font-weight: 400;\">Adaptive joins (Ph\u00e9p n\u1ed1i th\u00edch \u1ee9ng): L\u00e0 m\u1ed9t c\u1ea3i ti\u1ebfn m\u1edbi cho ph\u00e9p SQL Server ch\u1ecdn gi\u1eefa Nested Loops joins v\u00e0 Hash joins trong th\u1eddi gian th\u1ef1c, d\u1ef1a tr\u00ean s\u1ed1 l\u01b0\u1ee3ng h\u00e0ng th\u1ef1c t\u1ebf \u0111\u01b0\u1ee3c x\u1eed l\u00fd. \u0110i\u1ec1u n\u00e0y gi\u00fap t\u1ed1i \u01b0u h\u00f3a hi\u1ec7u su\u1ea5t c\u1ee7a c\u00e1c truy v\u1ea5n trong c\u00e1c t\u00ecnh hu\u1ed1ng m\u00e0 s\u1ed1 l\u01b0\u1ee3ng h\u00e0ng c\u00f3 th\u1ec3 thay \u0111\u1ed5i \u0111\u00e1ng k\u1ec3.<\/span><\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-ngoai-join-trong-sql-thi-con-cach-nao-k\u1ebft-h\u1ee3p-d\u1eef-li\u1ec7u-t\u1eeb-nhi\u1ec1u-b\u1ea3ng-khong\"><b>Ngo\u00e0i JOIN trong SQL th\u00ec c\u00f2n c\u00e1ch n\u00e0o k\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb nhi\u1ec1u b\u1ea3ng kh\u00f4ng?<\/b><\/h3>\n\n\n\n<p><span style=\"font-weight: 400;\">Ngo\u00e0i vi\u1ec7c s\u1eed d\u1ee5ng c\u00e1c ph\u00e9p JOIN, ta c\u00f2n c\u00f3 th\u1ec3 k\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb nhi\u1ec1u b\u1ea3ng b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng ph\u00e9p UNION. S\u1ef1 kh\u00e1c bi\u1ec7t c\u01a1 b\u1ea3n gi\u1eefa hai ph\u01b0\u01a1ng ph\u00e1p n\u00e0y l\u00e0 trong c\u00e2u l\u1ec7nh JOIN k\u1ebft h\u1ee3p c\u00e1c C\u1ed8T t\u1eeb c\u00e1c b\u1ea3ng kh\u00e1c nhau (d\u1ef1a tr\u00ean m\u1ed9t c\u1ed9t li\u00ean quan), trong khi v\u1edbi UNION k\u1ebft h\u1ee3p c\u00e1c D\u00d2NG t\u1eeb c\u00e1c b\u1ea3ng c\u00f3 c\u1ed9t gi\u1ed1ng nhau.&nbsp;<\/span><\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-co-th\u1ec3-k\u1ebft-h\u1ee3p-hai-b\u1ea3ng-ma-khong-co-m\u1ed1i-quan-h\u1ec7-khoa-chinh-va-khoa-ngo\u1ea1i-khong\"><b>C\u00f3 th\u1ec3 k\u1ebft h\u1ee3p hai b\u1ea3ng m\u00e0 kh\u00f4ng c\u00f3 m\u1ed1i quan h\u1ec7 kh\u00f3a ch\u00ednh v\u00e0 kh\u00f3a ngo\u1ea1i kh\u00f4ng?<\/b><\/h3>\n\n\n\n<p><span style=\"font-weight: 400;\">C\u00f3 th\u1ec3 k\u1ebft h\u1ee3p hai b\u1ea3ng m\u00e0 kh\u00f4ng c\u1ea7n m\u1ed1i quan h\u1ec7 kh\u00f3a ch\u00ednh v\u00e0 kh\u00f3a ngo\u1ea1i. \u0110i\u1ec1u n\u00e0y th\u01b0\u1eddng \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n th\u00f4ng qua c\u00e1c \u0111i\u1ec1u ki\u1ec7n kh\u00e1c nhau, ch\u1eb3ng h\u1ea1n nh\u01b0 c\u00e1c \u0111i\u1ec1u ki\u1ec7n so s\u00e1nh gi\u1eefa c\u00e1c c\u1ed9t trong hai b\u1ea3ng. Tuy nhi\u00ean, vi\u1ec7c s\u1eed d\u1ee5ng c\u00e1c m\u1ed1i quan h\u1ec7 kh\u00f3a ch\u00ednh v\u00e0 kh\u00f3a ngo\u1ea1i th\u01b0\u1eddng gi\u00fap qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3 h\u01a1n v\u00e0 gi\u1ea3m thi\u1ec3u s\u1ef1 ph\u1ee9c t\u1ea1p trong vi\u1ec7c truy v\u1ea5n d\u1eef li\u1ec7u.<\/span><\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>Xem th\u00eam: Danh s\u00e1ch <a href=\"https:\/\/itviec.com\/viec-lam-it\/sql?utm_medium=anchor_text_low&amp;utm_source=blog&amp;utm_campaign=viec_lam_sql&amp;utm_content=join_trong_sql\">vi\u1ec7c l\u00e0m SQL<\/a> m\u1edbi nh\u1ea5t tr\u00ean ITviec<\/strong><\/p>\n<\/blockquote>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-t\u1ed5ng-k\u1ebft-cach-s\u1eed-d\u1ee5ng-join-trong-sql\"><span class=\"ez-toc-section\" id=\"Tong_ket_cach_su_dung_JOIN_trong_SQL\"><\/span><b>T\u1ed5ng k\u1ebft c\u00e1ch s\u1eed d\u1ee5ng JOIN trong SQL<\/b><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p><span style=\"font-weight: 400;\">Nh\u01b0 v\u1eady, qua b\u00e0i vi\u1ebft n\u00e0y, ch\u00fang ta \u0111\u00e3 c\u00f3 c\u01a1 h\u1ed9i t\u00ecm hi\u1ec3u v\u1ec1 s\u1ee9c m\u1ea1nh v\u00e0 t\u1ea7m quan tr\u1ecdng c\u1ee7a c\u00e1c ph\u00e9p join trong SQL. T\u1eeb INNER JOIN \u0111\u1ebfn LEFT, RIGHT, FULL JOIN v\u00e0 CROSS JOIN, m\u1ed7i lo\u1ea1i join \u0111\u1ec1u mang l\u1ea1i nh\u1eefng c\u00e1ch ti\u1ebfp c\u1eadn ri\u00eang \u0111\u1ec3 k\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb c\u00e1c b\u1ea3ng kh\u00e1c nhau.<\/span><\/p>\n\n\n\n<p><span style=\"font-weight: 400;\">Vi\u1ec7c hi\u1ec3u r\u00f5 v\u1ec1 c\u00e1ch ho\u1ea1t \u0111\u1ed9ng c\u1ee7a ch\u00fang s\u1ebd gi\u00fap c\u00e1c chuy\u00ean vi\u00ean ph\u00e2n t\u00edch d\u1eef li\u1ec7u v\u00e0 ph\u00e1t tri\u1ec3n \u1ee9ng d\u1ee5ng t\u01b0\u01a1ng t\u00e1c v\u1edbi d\u1eef li\u1ec7u hi\u1ec7u qu\u1ea3 h\u01a1n v\u1edbi kh\u1ea3 n\u0103ng truy v\u1ea5n v\u00e0 x\u1eed l\u00fd d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch linh ho\u1ea1t v\u00e0 ch\u00ednh x\u00e1c. <\/span><span style=\"font-weight: 400;\">ITviec hy v\u1ecdng b\u00e0i vi\u1ebft tr\u00ean \u0111\u00e3 cung c\u1ea5p cho b\u1ea1n nh\u1eefng th\u00f4ng tin c\u1ea7n thi\u1ebft v\u1ec1 c\u00fa ph\u00e1p v\u00e0 c\u00e1ch s\u1eed d\u1ee5ng c\u00e1c ph\u00e9p JOIN trong SQL.<\/span><\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>\u0110\u1ecdc th\u00eam c\u00e1c b\u00e0i vi\u1ebft v\u1ec3 SQL n\u1ed5i b\u1eadt nh\u01b0:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><a href=\"https:\/\/itviec.com\/blog\/trigger-trong-sql\/\" target=\"_blank\" rel=\"noreferrer noopener\">Trigger trong SQL: Chi ti\u1ebft c\u00e1c thao t\u00e1c trigger SQL c\u01a1 b\u1ea3n<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/itviec.com\/blog\/sql-injection-la-gi\/\" target=\"_blank\" rel=\"noreferrer noopener\">SQL Injection: C\u00e1ch th\u1ee9c ho\u1ea1t \u0111\u1ed9ng v\u00e0 ph\u00f2ng ch\u1ed1ng SQLi<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/itviec.com\/blog\/function-trong-sql\/\" target=\"_blank\" rel=\"noreferrer noopener\">T\u1ed5ng h\u1ee3p 90+ function trong SQL c\u1ea7n bi\u1ebft<\/a><\/li>\n<\/ul>\n\n\n\n<p>V\u00e0 \u00f4n t\u1eadp th\u1eadt k\u1ef9 \u0111\u1ec3 ph\u1ecfng v\u1ea5n t\u1ef1 tin v\u1edbi&nbsp;<a href=\"https:\/\/itviec.com\/blog\/cau-hoi-phong-van-sql\/\" target=\"_blank\" rel=\"noreferrer noopener\">Top 30+ c\u00e2u h\u1ecfi ph\u1ecfng v\u1ea5n SQL ph\u1ed5 bi\u1ebfn nh\u1ea5t<\/a>&nbsp;nh\u00e9!<\/p>\n<\/blockquote>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Ph\u00e9p JOIN trong SQL l\u00e0 c\u00f4ng c\u1ee5 m\u1ea1nh m\u1ebd gi\u00fap k\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb nhi\u1ec1u b\u1ea3ng, x\u00e2y d\u1ef1ng c\u00e1i nh\u00ecn to\u00e0n di\u1ec7n v\u00e0 ch\u00ednh x\u00e1c v\u1ec1 th\u00f4ng tin. Trong l\u0129nh v\u1ef1c d\u1eef li\u1ec7u, vi\u1ec7c k\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb nhi\u1ec1u b\u1ea3ng l\u00e0 r\u1ea5t quan tr\u1ecdng \u0111\u1ec3 c\u00f3 \u0111\u01b0\u1ee3c b\u1ee9c tranh t\u1ed5ng th\u1ec3. Trong b\u00e0i [&hellip;]<\/p>\n","protected":false},"author":209,"featured_media":74156,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_gspb_post_css":"","footnotes":""},"categories":[109],"tags":[],"class_list":["post-74151","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-chuyen-mon-it"],"blocksy_meta":[],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v26.8 (Yoast SEO v27.8) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>JOIN trong SQL: C\u00fa ph\u00e1p v\u00e0 c\u00e1ch s\u1eed d\u1ee5ng c\u00e1c ph\u00e9p JOIN - ITviec Blog<\/title>\n<meta name=\"description\" content=\"Kh\u00e1m ph\u00e1 c\u00e1c ph\u00e9p join trong SQL \u0111\u1ec3 t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 k\u1ebft h\u1ee3p d\u1eef li\u1ec7u hi\u1ec7u qu\u1ea3: INNER, LEFT, RIGHT v\u00e0 FULL JOIN,...\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/itviec.com\/blog\/join-trong-sql\/\" \/>\n<meta property=\"og:locale\" content=\"vi_VN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"JOIN trong SQL: C\u00fa ph\u00e1p v\u00e0 c\u00e1ch s\u1eed d\u1ee5ng c\u00e1c ph\u00e9p JOIN\" \/>\n<meta property=\"og:description\" content=\"Ph\u00e9p JOIN trong SQL l\u00e0 c\u00f4ng c\u1ee5 m\u1ea1nh m\u1ebd gi\u00fap k\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb nhi\u1ec1u b\u1ea3ng, x\u00e2y d\u1ef1ng c\u00e1i nh\u00ecn to\u00e0n di\u1ec7n v\u00e0 ch\u00ednh x\u00e1c v\u1ec1 th\u00f4ng tin. 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