{"id":28439,"date":"2025-05-21T15:45:29","date_gmt":"2025-05-21T08:45:29","guid":{"rendered":"https:\/\/interdata.vn\/blog\/?p=28439"},"modified":"2025-05-22T13:14:27","modified_gmt":"2025-05-22T06:14:27","slug":"khoa-chinh-la-gi","status":"publish","type":"post","link":"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/","title":{"rendered":"Kh\u00f3a ch\u00ednh l\u00e0 g\u00ec? T\u00ednh n\u0103ng, c\u00fa ph\u00e1p, v\u00ed d\u1ee5 Primary Key d\u1ec5 hi\u1ec3u"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_85 counter-hierarchy ez-toc-counter ez-toc-white ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">N\u1ed8I DUNG<\/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 eztoc-toggle-hide-by-default' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Khoa-chinh-la-gi\" >Kh\u00f3a ch\u00ednh 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:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Chuc-nang-noi-bat-cua-Khoa-chinh\" >Ch\u1ee9c n\u0103ng n\u1ed5i b\u1eadt c\u1ee7a Kh\u00f3a ch\u00ednh<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Dinh-danh-duy-nhat-ban-ghi\" >\u0110\u1ecbnh danh duy nh\u1ea5t b\u1ea3n ghi<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Dam-bao-tinh-toan-ven-du-lieu\" >\u0110\u1ea3m b\u1ea3o t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Nen-tang-cho-viec-thiet-lap-moi-quan-he\" >N\u1ec1n t\u1ea3ng cho vi\u1ec7c thi\u1ebft l\u1eadp m\u1ed1i quan h\u1ec7<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Cac-cu-phap-thao-tac-trong-Khoa-chinh\" >C\u00e1c c\u00fa ph\u00e1p thao t\u00e1c trong Kh\u00f3a ch\u00ednh<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Tao-Khoa-chinh\" >T\u1ea1o Kh\u00f3a ch\u00ednh<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Xoa-Khoa-chinh\" >X\u00f3a Kh\u00f3a ch\u00ednh<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Vo-hieu-hoa-Khoa-chinh-Disable\" >V\u00f4 hi\u1ec7u h\u00f3a Kh\u00f3a ch\u00ednh (Disable)<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Kich-hoat-Khoa-chinh-Enable\" >K\u00edch ho\u1ea1t Kh\u00f3a ch\u00ednh (Enable)<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Loi-ich-cua-Khoa-chinh\" >L\u1ee3i \u00edch c\u1ee7a Kh\u00f3a ch\u00ednh<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Dam-bao-tinh-duy-nhat-va-toan-ven-du-lieu\" >\u0110\u1ea3m b\u1ea3o t\u00ednh duy nh\u1ea5t v\u00e0 to\u00e0n v\u1eb9n d\u1eef li\u1ec7u<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Giup-truy-xuat-du-lieu-hieu-qua\" >Gi\u00fap truy xu\u1ea5t d\u1eef li\u1ec7u hi\u1ec7u qu\u1ea3<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Don-gian-hoa-viec-thiet-lap-moi-quan-he\" >\u0110\u01a1n gi\u1ea3n h\u00f3a vi\u1ec7c thi\u1ebft l\u1eadp m\u1ed1i quan h\u1ec7<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Ho-tro-thao-tac-du-lieu-Cap-nhatXoa\" >H\u1ed7 tr\u1ee3 thao t\u00e1c d\u1eef li\u1ec7u (C\u1eadp nh\u1eadt\/X\u00f3a)<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Nen-tang-cho-thiet-ke-CSDL-tot\" >N\u1ec1n t\u1ea3ng cho thi\u1ebft k\u1ebf CSDL t\u1ed1t<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Su-khac-biet-giua-Khoa-chinh-va-Khoa-ngoai\" >S\u1ef1 kh\u00e1c bi\u1ec7t gi\u1eefa Kh\u00f3a ch\u00ednh v\u00e0 Kh\u00f3a ngo\u1ea1i<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-18\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Muc-dich-va-Vai-tro\" >M\u1ee5c \u0111\u00edch v\u00e0 Vai tr\u00f2<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-19\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Dac-diem\" >\u0110\u1eb7c \u0111i\u1ec3m<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-20\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#So-luong-trong-Bang\" >S\u1ed1 l\u01b0\u1ee3ng trong B\u1ea3ng<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-21\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Vi-du-minh-hoa\" >V\u00ed d\u1ee5 minh h\u1ecda<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-22\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Cau-hoi-thuong-gap-ve-Khoa-chinh-Primary-Key\" >C\u00e2u h\u1ecfi th\u01b0\u1eddng g\u1eb7p v\u1ec1 Kh\u00f3a ch\u00ednh (Primary Key)<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-23\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Mot-bang-trong-co-so-du-lieu-co-the-co-bao-nhieu-Khoa-chinh\" >M\u1ed9t b\u1ea3ng trong c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u00f3 th\u1ec3 c\u00f3 bao nhi\u00eau Kh\u00f3a ch\u00ednh?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-24\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Khoa-chinh-co-phai-la-chi-muc-Index-khong\" >Kh\u00f3a ch\u00ednh c\u00f3 ph\u1ea3i l\u00e0 ch\u1ec9 m\u1ee5c (Index) kh\u00f4ng?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-25\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Lam-the-nao-de-chon-Khoa-chinh-phu-hop-nhat-cho-mot-bang-du-lieu\" >L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 ch\u1ecdn Kh\u00f3a ch\u00ednh ph\u00f9 h\u1ee3p nh\u1ea5t cho m\u1ed9t b\u1ea3ng d\u1eef li\u1ec7u?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-26\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Su-khac-nhau-giua-Khoa-chinh-va-Khoa-ung-vien-Candidate-Key-la-gi\" >S\u1ef1 kh\u00e1c nhau gi\u1eefa Kh\u00f3a ch\u00ednh v\u00e0 Kh\u00f3a \u1ee9ng vi\u00ean (Candidate Key) l\u00e0 g\u00ec?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-27\" href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/#Dieu-gi-se-xay-ra-voi-du-lieu-va-cau-truc-neu-mot-bang-khong-co-Khoa-chinh\" >\u0110i\u1ec1u g\u00ec s\u1ebd x\u1ea3y ra v\u1edbi d\u1eef li\u1ec7u v\u00e0 c\u1ea5u tr\u00fac n\u1ebfu m\u1ed9t b\u1ea3ng kh\u00f4ng c\u00f3 Kh\u00f3a ch\u00ednh?<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<p>Trong c\u01a1 s\u1edf d\u1eef li\u1ec7u, Kh\u00f3a ch\u00ednh (Primary Key) l\u00e0 n\u1ec1n t\u1ea3ng quan tr\u1ecdng gi\u00fap x\u00e1c \u0111\u1ecbnh, qu\u1ea3n l\u00fd v\u00e0 truy xu\u1ea5t th\u00f4ng tin m\u1ed9t c\u00e1ch ch\u00ednh x\u00e1c. Kh\u00f4ng ch\u1ec9 \u0111\u1ea3m b\u1ea3o t\u00ednh duy nh\u1ea5t cho m\u1ed7i b\u1ea3n ghi, kh\u00f3a ch\u00ednh c\u00f2n \u0111\u00f3ng vai tr\u00f2 then ch\u1ed1t trong vi\u1ec7c duy tr\u00ec to\u00e0n v\u1eb9n d\u1eef li\u1ec7u v\u00e0 thi\u1ebft l\u1eadp m\u1ed1i quan h\u1ec7 gi\u1eefa c\u00e1c b\u1ea3ng. B\u00e0i vi\u1ebft sau t\u1eeb InterData s\u1ebd gi\u00fap b\u1ea1n hi\u1ec3u r\u00f5 \u201c<a href=\"https:\/\/interdata.vn\/blog\/khoa-chinh-la-gi\/\"><strong>Kh\u00f3a ch\u00ednh l\u00e0 g\u00ec?<\/strong><\/a>\u201d, ch\u1ee9c n\u0103ng, l\u1ee3i \u00edch, c\u00fa ph\u00e1p c\u1ee7a kh\u00f3a ch\u00ednh v\u00e0 gi\u1ea3i \u0111\u00e1p nh\u1eefng c\u00e2u h\u1ecfi th\u01b0\u1eddng g\u1eb7p r\u00f5 r\u00e0ng, d\u1ec5 hi\u1ec3u cho ng\u01b0\u1eddi m\u1edbi b\u1eaft \u0111\u1ea7u.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Khoa-chinh-la-gi\"><\/span>Kh\u00f3a ch\u00ednh l\u00e0 g\u00ec?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><strong>Kh\u00f3a ch\u00ednh (Primary Key &#8211; PK)<\/strong> l\u00e0 m\u1ed9t ho\u1eb7c nhi\u1ec1u c\u1ed9t trong b\u1ea3ng c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 \u0111\u1ecbnh danh duy nh\u1ea5t m\u1ed7i h\u00e0ng (b\u1ea3n ghi) trong b\u1ea3ng \u0111\u00f3. Nh\u1edd c\u00f3 Kh\u00f3a ch\u00ednh, ch\u00fang ta lu\u00f4n c\u00f3 th\u1ec3 x\u00e1c \u0111\u1ecbnh ch\u00ednh x\u00e1c m\u1ed9t b\u1ea3n ghi c\u1ee5 th\u1ec3 gi\u1eefa v\u00f4 s\u1ed1 b\u1ea3n ghi kh\u00e1c, \u0111\u1ea3m b\u1ea3o t\u00ednh ri\u00eang bi\u1ec7t cho t\u1eebng m\u1ee5c d\u1eef li\u1ec7u.<\/p>\n<p>H\u00e3y h\u00ecnh dung \u0111\u01a1n gi\u1ea3n, Kh\u00f3a ch\u00ednh gi\u1ed1ng nh\u01b0 S\u1ed1 C\u0103n c\u01b0\u1edbc c\u00f4ng d\u00e2n (CCCD) c\u1ee7a m\u1ed7i ng\u01b0\u1eddi d\u00e2n Vi\u1ec7t Nam. M\u1ed7i ng\u01b0\u1eddi ch\u1ec9 c\u00f3 m\u1ed9t s\u1ed1 CCCD duy nh\u1ea5t, v\u00e0 s\u1ed1 n\u00e0y d\u00f9ng \u0111\u1ec3 ph\u00e2n bi\u1ec7t b\u1ea1n v\u1edbi h\u00e0ng tri\u1ec7u ng\u01b0\u1eddi kh\u00e1c. Trong c\u01a1 s\u1edf d\u1eef li\u1ec7u, Kh\u00f3a ch\u00ednh l\u00e0m \u0111\u00fang vai tr\u00f2 t\u01b0\u01a1ng t\u1ef1 cho m\u1ed7i d\u00f2ng d\u1eef li\u1ec7u.<\/p>\n<figure id=\"attachment_28927\" aria-describedby=\"caption-attachment-28927\" style=\"width: 800px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Khoa-chinh-la-gi-2.jpg\" alt=\" Kh\u00f3a ch\u00ednh l\u00e0 g\u00ec?\" width=\"800\" height=\"500\" class=\"size-full wp-image-28927\" title=\"\" srcset=\"https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Khoa-chinh-la-gi-2.jpg 800w, https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Khoa-chinh-la-gi-2-300x188.jpg 300w, https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Khoa-chinh-la-gi-2-768x480.jpg 768w, https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Khoa-chinh-la-gi-2-750x469.jpg 750w\" sizes=\"auto, (max-width: 800px) 100vw, 800px\" \/><figcaption id=\"caption-attachment-28927\" class=\"wp-caption-text\">Kh\u00f3a ch\u00ednh l\u00e0 g\u00ec?<\/figcaption><\/figure>\n<p>Vai tr\u00f2 ch\u00ednh v\u00e0 quan tr\u1ecdng nh\u1ea5t c\u1ee7a Kh\u00f3a ch\u00ednh l\u00e0 <strong>\u0111\u1ea3m b\u1ea3o t\u00ednh duy nh\u1ea5t cho m\u1ed7i b\u1ea3n ghi<\/strong>. N\u00f3 gi\u1ed1ng nh\u01b0 m\u1ed9t &#8220;b\u1ea3o v\u1ec7&#8221; ng\u0103n kh\u00f4ng cho hai b\u1ea3n ghi b\u1ea5t k\u1ef3 trong c\u00f9ng m\u1ed9t b\u1ea3ng c\u00f3 c\u00f9ng m\u1ed9t &#8220;danh t\u00ednh&#8221; \u0111\u1ecbnh danh.<\/p>\n<p>B\u1eb1ng vi\u1ec7c \u00e1p \u0111\u1eb7t r\u00e0ng bu\u1ed9c (constraint) Kh\u00f3a ch\u00ednh, h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u (DBMS &#8211; Database Management System) duy tr\u00ec \u0111\u01b0\u1ee3c t\u00ednh to\u00e0n v\u1eb9n c\u1ee7a d\u1eef li\u1ec7u (Data Integrity). N\u1ebfu ai \u0111\u00f3 c\u1ed1 g\u1eafng th\u00eam m\u1ed9t b\u1ea3n ghi c\u00f3 gi\u00e1 tr\u1ecb Kh\u00f3a ch\u00ednh \u0111\u00e3 t\u1ed3n t\u1ea1i, h\u1ec7 th\u1ed1ng s\u1ebd b\u00e1o l\u1ed7i ngay l\u1eadp t\u1ee9c, gi\u00fap d\u1eef li\u1ec7u lu\u00f4n ch\u00ednh x\u00e1c v\u00e0 nh\u1ea5t qu\u00e1n.<\/p>\n<p>Kh\u00f4ng ch\u1ec9 \u0111\u1ecbnh danh, Kh\u00f3a ch\u00ednh c\u00f2n \u0111\u00f3ng vai tr\u00f2 l\u00e0 &#8220;\u0111i\u1ec3m neo&#8221; \u0111\u1ec3 thi\u1ebft l\u1eadp m\u1ed1i quan h\u1ec7 gi\u1eefa c\u00e1c b\u1ea3ng kh\u00e1c nhau. M\u1ed9t b\u1ea3ng c\u00f3 th\u1ec3 tham chi\u1ebfu \u0111\u1ebfn m\u1ed9t b\u1ea3n ghi c\u1ee5 th\u1ec3 \u1edf b\u1ea3ng kh\u00e1c th\u00f4ng qua gi\u00e1 tr\u1ecb Kh\u00f3a ch\u00ednh c\u1ee7a b\u1ea3n ghi \u0111\u00f3, th\u01b0\u1eddng l\u00e0 d\u00f9ng m\u1ed9t c\u1ed9t g\u1ecdi l\u00e0 Kh\u00f3a ngo\u1ea1i (Foreign Key).<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Chuc-nang-noi-bat-cua-Khoa-chinh\"><\/span>Ch\u1ee9c n\u0103ng n\u1ed5i b\u1eadt c\u1ee7a Kh\u00f3a ch\u00ednh<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Kh\u00f3a ch\u00ednh (Primary Key) kh\u00f4ng ch\u1ec9 l\u00e0 m\u1ed9t kh\u00e1i ni\u1ec7m \u0111\u1ecbnh danh; n\u00f3 th\u1ef1c hi\u1ec7n nhi\u1ec1u ch\u1ee9c n\u0103ng thi\u1ebft y\u1ebfu \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o c\u01a1 s\u1edf d\u1eef li\u1ec7u ho\u1ea1t \u0111\u1ed9ng hi\u1ec7u qu\u1ea3 v\u00e0 ch\u00ednh x\u00e1c. Ch\u1ee9c n\u0103ng ch\u00ednh c\u1ee7a Kh\u00f3a ch\u00ednh l\u00e0 <strong>\u0111\u1ecbnh danh duy nh\u1ea5t<\/strong> c\u00e1c b\u1ea3n ghi, <strong>\u0111\u1ea3m b\u1ea3o t\u00ednh to\u00e0n v\u1eb9n<\/strong> c\u1ee7a d\u1eef li\u1ec7u v\u00e0 l\u00e0m <strong>n\u1ec1n t\u1ea3ng cho vi\u1ec7c thi\u1ebft l\u1eadp m\u1ed1i quan h\u1ec7<\/strong> gi\u1eefa c\u00e1c b\u1ea3ng.<\/p>\n<p>Nh\u1eefng ch\u1ee9c n\u0103ng n\u00e0y l\u00e0 c\u1ed1t l\u00f5i c\u1ee7a m\u00f4 h\u00ecnh c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7, gi\u00fap qu\u1ea3n l\u00fd l\u01b0\u1ee3ng l\u1edbn d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch c\u00f3 t\u1ed5 ch\u1ee9c v\u00e0 \u0111\u00e1ng tin c\u1eady. Vi\u1ec7c hi\u1ec3u r\u00f5 c\u00e1c ch\u1ee9c n\u0103ng n\u00e0y l\u00e0 r\u1ea5t quan tr\u1ecdng cho b\u1ea5t k\u1ef3 ai l\u00e0m vi\u1ec7c v\u1edbi c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Dinh-danh-duy-nhat-ban-ghi\"><\/span>\u0110\u1ecbnh danh duy nh\u1ea5t b\u1ea3n ghi<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Ch\u1ee9c n\u0103ng c\u01a1 b\u1ea3n v\u00e0 quan tr\u1ecdng nh\u1ea5t c\u1ee7a Kh\u00f3a ch\u00ednh l\u00e0 cung c\u1ea5p m\u1ed9t ph\u01b0\u01a1ng ti\u1ec7n \u0111\u1ec3 x\u00e1c \u0111\u1ecbnh <em>ch\u00ednh x\u00e1c<\/em> t\u1eebng h\u00e0ng (b\u1ea3n ghi) trong m\u1ed9t b\u1ea3ng. N\u00f3 \u0111\u1ea3m b\u1ea3o r\u1eb1ng kh\u00f4ng c\u00f3 hai b\u1ea3n ghi n\u00e0o trong c\u00f9ng m\u1ed9t b\u1ea3ng c\u00f3 c\u00f9ng m\u1ed9t gi\u00e1 tr\u1ecb Kh\u00f3a ch\u00ednh.<\/p>\n<p>\u0110i\u1ec1u n\u00e0y gi\u1ed1ng nh\u01b0 vi\u1ec7c m\u1ed7i h\u1ecdc sinh trong tr\u01b0\u1eddng c\u00f3 m\u1ed9t M\u00e3 s\u1ed1 h\u1ecdc sinh ri\u00eang bi\u1ec7t. D\u00f9 c\u00f3 hai h\u1ecdc sinh c\u00f9ng t\u00ean, c\u00f9ng ng\u00e0y sinh, m\u00e3 s\u1ed1 h\u1ecdc sinh duy nh\u1ea5t s\u1ebd gi\u00fap nh\u00e0 tr\u01b0\u1eddng ph\u00e2n bi\u1ec7t r\u00f5 r\u00e0ng \u0111\u00f3 l\u00e0 hai c\u00e1 th\u1ec3 kh\u00e1c nhau. Kh\u00f3a ch\u00ednh l\u00e0m y h\u1ec7t \u0111i\u1ec1u \u0111\u00f3 cho d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Dam-bao-tinh-toan-ven-du-lieu\"><\/span>\u0110\u1ea3m b\u1ea3o t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Vi\u1ec7c \u00e1p \u0111\u1eb7t r\u00e0ng bu\u1ed9c Kh\u00f3a ch\u00ednh (bao g\u1ed3m t\u00ednh Duy nh\u1ea5t v\u00e0 Kh\u00f4ng r\u1ed7ng) l\u00e0 m\u1ed9t c\u00e1ch m\u1ea1nh m\u1ebd \u0111\u1ec3 <strong>th\u1ef1c thi<\/strong> <strong>t\u00ednh to\u00e0n v\u1eb9n th\u1ef1c th\u1ec3<\/strong> (<a href=\"https:\/\/en.wikipedia.org\/wiki\/Entity_integrity\" target=\"_blank\" rel=\"noopener\">Entity Integrity<\/a>), m\u1ed9t nguy\u00ean t\u1eafc n\u1ec1n t\u1ea3ng c\u1ee7a c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7. N\u00f3 ng\u0103n ch\u1eb7n vi\u1ec7c nh\u1eadp d\u1eef li\u1ec7u kh\u00f4ng h\u1ee3p l\u1ec7 ho\u1eb7c m\u00e2u thu\u1eabn.<\/p>\n<p>H\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u (DBMS) s\u1ebd t\u1ef1 \u0111\u1ed9ng ki\u1ec3m tra r\u00e0ng bu\u1ed9c n\u00e0y m\u1ed7i khi c\u00f3 thao t\u00e1c th\u00eam ho\u1eb7c s\u1eeda d\u1eef li\u1ec7u. N\u1ebfu b\u1ea3n ghi m\u1edbi ho\u1eb7c b\u1ea3n ghi \u0111\u01b0\u1ee3c s\u1eeda vi ph\u1ea1m t\u00ednh duy nh\u1ea5t ho\u1eb7c kh\u00f4ng r\u1ed7ng c\u1ee7a Kh\u00f3a ch\u00ednh, thao t\u00e1c s\u1ebd b\u1ecb t\u1eeb ch\u1ed1i. \u0110i\u1ec1u n\u00e0y \u0111\u1ea3m b\u1ea3o d\u1eef li\u1ec7u trong b\u1ea3ng lu\u00f4n s\u1ea1ch v\u00e0 \u0111\u00e1ng tin c\u1eady.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Nen-tang-cho-viec-thiet-lap-moi-quan-he\"><\/span>N\u1ec1n t\u1ea3ng cho vi\u1ec7c thi\u1ebft l\u1eadp m\u1ed1i quan h\u1ec7<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Ch\u1ee9c n\u0103ng quan tr\u1ecdng th\u1ee9 ba l\u00e0 Kh\u00f3a ch\u00ednh \u0111\u00f3ng vai tr\u00f2 l\u00e0 &#8220;\u0111\u00edch&#8221; m\u00e0 Kh\u00f3a ngo\u1ea1i (Foreign Key) c\u1ee7a c\u00e1c b\u1ea3ng kh\u00e1c s\u1ebd tham chi\u1ebfu t\u1edbi. \u0110\u00e2y l\u00e0 c\u00e1ch c\u01a1 b\u1ea3n \u0111\u1ec3 li\u00ean k\u1ebft th\u00f4ng tin gi\u1eefa c\u00e1c b\u1ea3ng kh\u00e1c nhau trong c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7, t\u1ea1o n\u00ean s\u1ef1 k\u1ebft n\u1ed1i logic gi\u1eefa c\u00e1c t\u1eadp d\u1eef li\u1ec7u.<\/p>\n<p>V\u00ed d\u1ee5 \u0111i\u1ec3n h\u00ecnh l\u00e0 m\u1ed1i quan h\u1ec7 gi\u1eefa b\u1ea3ng <code>KHACH_HANG<\/code> (c\u00f3 <code>MaKH<\/code> l\u00e0 Kh\u00f3a ch\u00ednh) v\u00e0 b\u1ea3ng <code>DON_HANG<\/code>. B\u1ea3ng <code>DON_HANG<\/code> s\u1ebd c\u00f3 c\u1ed9t <code>MaKH<\/code> l\u00e0m Kh\u00f3a ngo\u1ea1i. Gi\u00e1 tr\u1ecb trong c\u1ed9t Kh\u00f3a ngo\u1ea1i <code>MaKH<\/code> c\u1ee7a b\u1ea3ng <code>DON_HANG<\/code> s\u1ebd ch\u1ec9 \u0111\u01b0\u1ee3c ph\u00e9p l\u00e0 gi\u00e1 tr\u1ecb t\u1ed3n t\u1ea1i trong c\u1ed9t Kh\u00f3a ch\u00ednh <code>MaKH<\/code> c\u1ee7a b\u1ea3ng <code>KHACH_HANG<\/code>. \u0110i\u1ec1u n\u00e0y li\u00ean k\u1ebft m\u1ed7i \u0111\u01a1n h\u00e0ng v\u1edbi kh\u00e1ch h\u00e0ng c\u1ee5 th\u1ec3 \u0111\u00e3 \u0111\u1eb7t n\u00f3.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Cac-cu-phap-thao-tac-trong-Khoa-chinh\"><\/span>C\u00e1c c\u00fa ph\u00e1p thao t\u00e1c trong Kh\u00f3a ch\u00ednh<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>\u0110\u1ec3 l\u00e0m vi\u1ec7c hi\u1ec7u qu\u1ea3 v\u1edbi Kh\u00f3a ch\u00ednh (Primary Key) trong c\u00e1c h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u, b\u1ea1n c\u1ea7n n\u1eafm v\u1eefng c\u00e1c c\u00e2u l\u1ec7nh SQL cho ph\u00e9p t\u1ea1o m\u1edbi, lo\u1ea1i b\u1ecf, v\u00e0 trong m\u1ed9t s\u1ed1 tr\u01b0\u1eddng h\u1ee3p \u0111\u1eb7c bi\u1ec7t, t\u1ea1m th\u1eddi t\u1eaft ho\u1eb7c b\u1eadt l\u1ea1i Kh\u00f3a ch\u00ednh. Vi\u1ec7c thao t\u00e1c \u0111\u00fang c\u00fa ph\u00e1p l\u00e0 n\u1ec1n t\u1ea3ng \u0111\u1ec3 qu\u1ea3n l\u00fd <a href=\"https:\/\/interdata.vn\/blog\/cau-truc-du-lieu\/\">c\u1ea5u tr\u00fac d\u1eef li\u1ec7u<\/a> m\u1ed9t c\u00e1ch ch\u00ednh x\u00e1c v\u00e0 an to\u00e0n.<\/p>\n<p>C\u00e1c thao t\u00e1c n\u00e0y ch\u1ee7 y\u1ebfu \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n th\u00f4ng qua l\u1ec7nh <code>CREATE TABLE<\/code> (khi t\u1ea1o b\u1ea3ng) v\u00e0 <code>ALTER TABLE<\/code> (khi ch\u1ec9nh s\u1eeda b\u1ea3ng \u0111\u00e3 t\u1ed3n t\u1ea1i). D\u01b0\u1edbi \u0111\u00e2y l\u00e0 chi ti\u1ebft v\u1ec1 c\u00e1c c\u00fa ph\u00e1p n\u00e0y.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Tao-Khoa-chinh\"><\/span>T\u1ea1o Kh\u00f3a ch\u00ednh<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Kh\u00f3a ch\u00ednh th\u01b0\u1eddng \u0111\u01b0\u1ee3c t\u1ea1o c\u00f9ng l\u00fac khi \u0111\u1ecbnh ngh\u0129a b\u1ea3ng m\u1edbi th\u00f4ng qua c\u00fa ph\u00e1p <code>CREATE TABLE<\/code>, s\u1eed d\u1ee5ng t\u1eeb kh\u00f3a <code>PRIMARY KEY<\/code> sau \u0111\u1ecbnh ngh\u0129a c\u1ed9t. Ngo\u00e0i ra, b\u1ea1n ho\u00e0n to\u00e0n c\u00f3 th\u1ec3 th\u00eam Kh\u00f3a ch\u00ednh v\u00e0o m\u1ed9t b\u1ea3ng \u0111\u00e3 t\u1ed3n t\u1ea1i b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng c\u00e2u l\u1ec7nh <code>ALTER TABLE<\/code> k\u1ebft h\u1ee3p v\u1edbi m\u1ec7nh \u0111\u1ec1 <code>ADD CONSTRAINT<\/code>.<\/p>\n<p>T\u1ea1o kh\u00f3a ch\u00ednh b\u1eb1ng c\u00fa ph\u00e1p CREATE TABLE<\/p>\n<pre>CREATE TABLE ten_bang ( cot1 kieu_du_lieu [ NULL | NOT NULL ] [ PRIMARY KEY ] ,cot2 kieu_du_lieu [ NULL | NOT NULL ] ,\u2026);<\/pre>\n<p>T\u1ea1o kh\u00f3a ch\u00ednh b\u1eb1ng c\u00fa ph\u00e1p ALTER TABLE<\/p>\n<pre>ALTER TABLE ten_bang ADD CONSTRAINT ten_rang_buoc PRIMARY KEY ( cot1, cot2, \u2026 cot_n)<\/pre>\n<h3><span class=\"ez-toc-section\" id=\"Xoa-Khoa-chinh\"><\/span>X\u00f3a Kh\u00f3a ch\u00ednh<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>N\u1ebfu c\u1ea7n g\u1ee1 b\u1ecf r\u00e0ng bu\u1ed9c Kh\u00f3a ch\u00ednh kh\u1ecfi m\u1ed9t b\u1ea3ng, b\u1ea1n s\u1eed d\u1ee5ng c\u00e2u l\u1ec7nh <code>ALTER TABLE<\/code> c\u00f9ng v\u1edbi m\u1ec7nh \u0111\u1ec1 <code>DROP CONSTRAINT<\/code>. Thao t\u00e1c n\u00e0y y\u00eau c\u1ea7u b\u1ea1n bi\u1ebft ch\u00ednh x\u00e1c t\u00ean c\u1ee7a r\u00e0ng bu\u1ed9c Kh\u00f3a ch\u00ednh \u0111\u00e3 \u0111\u01b0\u1ee3c \u0111\u1eb7t khi t\u1ea1o ho\u1eb7c th\u00eam n\u00f3 v\u00e0o b\u1ea3ng.<\/p>\n<pre>ALTER TABLE ten_bang DROP CONSTRAINT ten_rang_buoc;<\/pre>\n<p><strong>V\u00ed d\u1ee5<\/strong>: X\u00f3a Kh\u00f3a ch\u00ednh c\u00f3 t\u00ean <code>PK_KhachHang<\/code> kh\u1ecfi b\u1ea3ng <code>KHACH_HANG<\/code>:<\/p>\n<pre>ALTER TABLE KHACH_HANG\r\nDROP CONSTRAINT PK_KhachHang;<\/pre>\n<p>Sau khi th\u1ef1c hi\u1ec7n l\u1ec7nh n\u00e0y, r\u00e0ng bu\u1ed9c Duy nh\u1ea5t v\u00e0 Kh\u00f4ng r\u1ed7ng tr\u00ean c\u1ed9t <code>MaKH<\/code> (n\u1ebfu n\u00f3 l\u00e0 Kh\u00f3a ch\u00ednh duy nh\u1ea5t) s\u1ebd b\u1ecb g\u1ee1 b\u1ecf. Tuy nhi\u00ean, b\u1ea3n th\u00e2n c\u1ed9t <code>MaKH<\/code> v\u00e0 d\u1eef li\u1ec7u trong \u0111\u00f3 v\u1eabn t\u1ed3n t\u1ea1i.<\/p>\n<figure id=\"attachment_28926\" aria-describedby=\"caption-attachment-28926\" style=\"width: 800px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Cac-cu-phap-thao-tac-trong-Khoa-chinh-2.jpg\" alt=\" C\u00e1c c\u00fa ph\u00e1p thao t\u00e1c trong Kh\u00f3a ch\u00ednh\" width=\"800\" height=\"500\" class=\"size-full wp-image-28926\" title=\"\" srcset=\"https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Cac-cu-phap-thao-tac-trong-Khoa-chinh-2.jpg 800w, https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Cac-cu-phap-thao-tac-trong-Khoa-chinh-2-300x188.jpg 300w, https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Cac-cu-phap-thao-tac-trong-Khoa-chinh-2-768x480.jpg 768w, https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Cac-cu-phap-thao-tac-trong-Khoa-chinh-2-750x469.jpg 750w\" sizes=\"auto, (max-width: 800px) 100vw, 800px\" \/><figcaption id=\"caption-attachment-28926\" class=\"wp-caption-text\">C\u00e1c c\u00fa ph\u00e1p thao t\u00e1c trong Kh\u00f3a ch\u00ednh<\/figcaption><\/figure>\n<h3><span class=\"ez-toc-section\" id=\"Vo-hieu-hoa-Khoa-chinh-Disable\"><\/span>V\u00f4 hi\u1ec7u h\u00f3a Kh\u00f3a ch\u00ednh (Disable)<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Trong m\u1ed9t s\u1ed1 tr\u01b0\u1eddng h\u1ee3p \u0111\u1eb7c bi\u1ec7t, v\u00ed d\u1ee5 khi th\u1ef1c hi\u1ec7n nh\u1eadp d\u1eef li\u1ec7u s\u1ed1 l\u01b0\u1ee3ng r\u1ea5t l\u1edbn (bulk insert) m\u00e0 b\u1ea1n \u0111\u00e3 <em>ch\u1eafc ch\u1eafn<\/em> d\u1eef li\u1ec7u ngu\u1ed3n kh\u00f4ng vi ph\u1ea1m r\u00e0ng bu\u1ed9c, b\u1ea1n c\u00f3 th\u1ec3 t\u1ea1m th\u1eddi v\u00f4 hi\u1ec7u h\u00f3a (disable) Kh\u00f3a ch\u00ednh. \u0110i\u1ec1u n\u00e0y gi\u00fap qu\u00e1 tr\u00ecnh nh\u1eadp li\u1ec7u nhanh h\u01a1n v\u00ec h\u1ec7 th\u1ed1ng kh\u00f4ng ki\u1ec3m tra r\u00e0ng bu\u1ed9c li\u00ean t\u1ee5c tr\u00ean m\u1ed7i d\u00f2ng.<\/p>\n<p>C\u00fa ph\u00e1p \u0111\u1ec3 v\u00f4 hi\u1ec7u h\u00f3a r\u00e0ng bu\u1ed9c Kh\u00f3a ch\u00ednh th\u01b0\u1eddng s\u1eed d\u1ee5ng <code>ALTER TABLE.<\/code><\/p>\n<pre>ALTER INDEX ten_rang_buoc ON ten_bang\r\n\r\nDISABLE;<\/pre>\n<p><strong>V\u00ed d\u1ee5<\/strong>: V\u00f4 hi\u1ec7u h\u00f3a kh\u00f3a ch\u00ednh <code>nhanvien_pk<\/code> trong b\u1ea3ng <code>nhanvien<\/code>.<\/p>\n<pre>ALTER INDEX nhanvien_pk ON nhanvien\r\nDISABLE;<\/pre>\n<h3><span class=\"ez-toc-section\" id=\"Kich-hoat-Khoa-chinh-Enable\"><\/span>K\u00edch ho\u1ea1t Kh\u00f3a ch\u00ednh (Enable)<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Sau khi ho\u00e0n t\u1ea5t qu\u00e1 tr\u00ecnh c\u1ea7n thi\u1ebft (nh\u01b0 nh\u1eadp li\u1ec7u s\u1ed1 l\u01b0\u1ee3ng l\u1edbn), b\u1ea1n ph\u1ea3i k\u00edch ho\u1ea1t l\u1ea1i (enable) Kh\u00f3a ch\u00ednh \u0111\u1ec3 h\u1ec7 th\u1ed1ng ti\u1ebfp t\u1ee5c ki\u1ec3m tra v\u00e0 \u0111\u1ea3m b\u1ea3o t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u cho c\u00e1c thao t\u00e1c sau n\u00e0y. Qu\u00e1 tr\u00ecnh k\u00edch ho\u1ea1t th\u01b0\u1eddng bao g\u1ed3m ki\u1ec3m tra l\u1ea1i to\u00e0n b\u1ed9 d\u1eef li\u1ec7u hi\u1ec7n c\u00f3 trong c\u1ed9t Kh\u00f3a ch\u00ednh xem c\u00f3 vi ph\u1ea1m n\u00e0o kh\u00f4ng.<\/p>\n<p>C\u00fa ph\u00e1p \u0111\u1ec3 k\u00edch ho\u1ea1t l\u1ea1i Kh\u00f3a ch\u00ednh c\u0169ng d\u00f9ng <code>ALTER TABLE<\/code>. L\u1ec7nh n\u00e0y s\u1ebd b\u1eadt l\u1ea1i ki\u1ec3m tra r\u00e0ng bu\u1ed9c v\u00e0 c\u00f3 th\u1ec3 qu\u00e9t qua d\u1eef li\u1ec7u hi\u1ec7n t\u1ea1i \u0111\u1ec3 t\u00ecm vi ph\u1ea1m n\u1ebfu c\u00f3.<\/p>\n<pre>ALTER INDEX ten_rang_buoc ON ten_bang\r\n\r\nREBUILD;<\/pre>\n<p><strong>V\u00ed d\u1ee5<\/strong>: K\u00edch ho\u1ea1t l\u1ea1i Kh\u00f3a ch\u00ednh t\u00ean <code>nhanvien_pk<\/code> tr\u00ean b\u1ea3ng <code>nhanvien<\/code>:<\/p>\n<pre><code>ALTER INDEX nhanvien_pk ON nhanvien\r\nREBUILD;<\/code><\/pre>\n<p><strong>L\u01b0u \u00fd quan tr\u1ecdng<\/strong>: Vi\u1ec7c v\u00f4 hi\u1ec7u h\u00f3a Kh\u00f3a ch\u00ednh n\u00ean \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n h\u1ebft s\u1ee9c th\u1eadn tr\u1ecdng v\u00e0 ch\u1ec9 khi th\u1ef1c s\u1ef1 c\u1ea7n thi\u1ebft, v\u00ec n\u00f3 t\u1ea1m th\u1eddi lo\u1ea1i b\u1ecf l\u1edbp b\u1ea3o v\u1ec7 to\u00e0n v\u1eb9n d\u1eef li\u1ec7u quan tr\u1ecdng. Lu\u00f4n \u0111\u1ea3m b\u1ea3o k\u00edch ho\u1ea1t l\u1ea1i Kh\u00f3a ch\u00ednh ngay sau khi ho\u00e0n th\u00e0nh c\u00f4ng vi\u1ec7c v\u00e0 x\u1eed l\u00fd b\u1ea5t k\u1ef3 l\u1ed7i vi ph\u1ea1m n\u00e0o \u0111\u01b0\u1ee3c ph\u00e1t hi\u1ec7n trong qu\u00e1 tr\u00ecnh k\u00edch ho\u1ea1t \u0111\u1ec3 d\u1eef li\u1ec7u lu\u00f4n ch\u00ednh x\u00e1c.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Loi-ich-cua-Khoa-chinh\"><\/span>L\u1ee3i \u00edch c\u1ee7a Kh\u00f3a ch\u00ednh<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Vi\u1ec7c s\u1eed d\u1ee5ng Kh\u00f3a ch\u00ednh (Primary Key) kh\u00f4ng ch\u1ec9 \u0111\u01a1n thu\u1ea7n l\u00e0 m\u1ed9t quy t\u1eafc trong thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u, m\u00e0 n\u00f3 mang l\u1ea1i nhi\u1ec1u l\u1ee3i \u00edch thi\u1ebft y\u1ebfu, gi\u00fap h\u1ec7 th\u1ed1ng d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n m\u1ea1nh m\u1ebd, \u0111\u00e1ng tin c\u1eady v\u00e0 ho\u1ea1t \u0111\u1ed9ng hi\u1ec7u qu\u1ea3 h\u01a1n. N\u1eafm r\u00f5 nh\u1eefng \u01b0u \u0111i\u1ec3m c\u1ee7a kh\u00f3a ch\u00ednh l\u00e0 g\u00ec s\u1ebd gi\u00fap b\u1ea1n th\u1ea5y \u0111\u01b0\u1ee3c t\u1ea7m quan tr\u1ecdng c\u1ee7a vi\u1ec7c \u0111\u1ecbnh ngh\u0129a Kh\u00f3a ch\u00ednh \u0111\u00fang \u0111\u1eafn.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Dam-bao-tinh-duy-nhat-va-toan-ven-du-lieu\"><\/span>\u0110\u1ea3m b\u1ea3o t\u00ednh duy nh\u1ea5t v\u00e0 to\u00e0n v\u1eb9n d\u1eef li\u1ec7u<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>\u01afu \u0111i\u1ec3m c\u01a1 b\u1ea3n v\u00e0 quan tr\u1ecdng nh\u1ea5t l\u00e0 Kh\u00f3a ch\u00ednh tr\u1ef1c ti\u1ebfp \u0111\u1ea3m b\u1ea3o <strong>t\u00ednh duy nh\u1ea5t<\/strong> cho m\u1ed7i b\u1ea3n ghi. N\u00f3 gi\u1ed1ng nh\u01b0 vi\u1ec7c m\u1ed7i s\u1ea3n ph\u1ea9m trong kho \u0111\u1ec1u c\u00f3 m\u1ed9t m\u00e3 v\u1ea1ch ri\u00eang bi\u1ec7t. \u0110i\u1ec1u n\u00e0y ng\u0103n ch\u1eb7n ho\u00e0n to\u00e0n t\u00ecnh tr\u1ea1ng d\u1eef li\u1ec7u b\u1ecb tr\u00f9ng l\u1eb7p, m\u1ed9t v\u1ea5n \u0111\u1ec1 nghi\u00eam tr\u1ecdng c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn sai s\u00f3t trong b\u00e1o c\u00e1o v\u00e0 ph\u00e2n t\u00edch.<\/p>\n<p>B\u00ean c\u1ea1nh t\u00ednh duy nh\u1ea5t, r\u00e0ng bu\u1ed9c Kh\u00f3a ch\u00ednh c\u00f2n th\u1ef1c thi t\u00ednh <strong>Kh\u00f4ng r\u1ed7ng (Not Null)<\/strong>. \u0110i\u1ec1u n\u00e0y \u0111\u1ea3m b\u1ea3o r\u1eb1ng m\u1ecdi b\u1ea3n ghi \u0111\u1ec1u c\u00f3 m\u1ed9t gi\u00e1 tr\u1ecb \u0111\u1ecbnh danh, kh\u00f4ng b\u1ecb b\u1ecf tr\u1ed1ng. Nh\u1edd hai \u0111\u1eb7c \u0111i\u1ec3m n\u00e0y, Kh\u00f3a ch\u00ednh g\u00f3p ph\u1ea7n c\u1ed1t l\u00f5i v\u00e0o vi\u1ec7c duy tr\u00ec <strong>t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u<\/strong> (Data Integrity) trong to\u00e0n b\u1ed9 b\u1ea3ng.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Giup-truy-xuat-du-lieu-hieu-qua\"><\/span>Gi\u00fap truy xu\u1ea5t d\u1eef li\u1ec7u hi\u1ec7u qu\u1ea3<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>M\u1ed9t l\u1ee3i \u00edch k\u1ef9 thu\u1eadt r\u1ea5t quan tr\u1ecdng l\u00e0 h\u1ea7u h\u1ebft c\u00e1c h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u (DBMS) s\u1ebd t\u1ef1 \u0111\u1ed9ng t\u1ea1o m\u1ed9t <strong>ch\u1ec9 m\u1ee5c (Index)<\/strong> tr\u00ean c\u1ed9t ho\u1eb7c t\u1eadp h\u1ee3p c\u1ed9t \u0111\u01b0\u1ee3c ch\u1ecdn l\u00e0m Kh\u00f3a ch\u00ednh. Ch\u1ec9 m\u1ee5c n\u00e0y ho\u1ea1t \u0111\u1ed9ng gi\u1ed1ng nh\u01b0 m\u1ed9t m\u1ee5c l\u1ee5c \u0111\u01b0\u1ee3c s\u1eafp x\u1ebfp c\u1ee7a b\u1ea3ng, gi\u00fap h\u1ec7 th\u1ed1ng t\u00ecm ki\u1ebfm v\u00e0 truy xu\u1ea5t m\u1ed9t b\u1ea3n ghi c\u1ee5 th\u1ec3 d\u1ef1a tr\u00ean gi\u00e1 tr\u1ecb Kh\u00f3a ch\u00ednh nhanh h\u01a1n r\u1ea5t k\u1ec3.<\/p>\n<p>V\u00ed d\u1ee5, n\u1ebfu b\u1ea1n mu\u1ed1n t\u00ecm th\u00f4ng tin chi ti\u1ebft c\u1ee7a \u0110\u01a1n h\u00e0ng c\u00f3 m\u00e3 s\u1ed1 <code>DH12345<\/code>, vi\u1ec7c t\u00ecm ki\u1ebfm tr\u00ean c\u1ed9t <code>MaDonHang<\/code> (n\u1ebfu l\u00e0 Kh\u00f3a ch\u00ednh c\u00f3 ch\u1ec9 m\u1ee5c) s\u1ebd c\u1ef1c k\u1ef3 nhanh. H\u1ec7 th\u1ed1ng kh\u00f4ng c\u1ea7n duy\u1ec7t qua h\u00e0ng tri\u1ec7u \u0111\u01a1n h\u00e0ng kh\u00e1c m\u00e0 c\u00f3 th\u1ec3 \u0111i th\u1eb3ng \u0111\u1ebfn v\u1ecb tr\u00ed c\u1ee7a <code>DH12345<\/code>, ti\u1ebft ki\u1ec7m th\u1eddi gian v\u00e0 t\u00e0i nguy\u00ean x\u1eed l\u00fd.<\/p>\n<figure id=\"attachment_28925\" aria-describedby=\"caption-attachment-28925\" style=\"width: 800px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Loi-ich-cua-Khoa-chinh-2.jpg\" alt=\" L\u1ee3i \u00edch c\u1ee7a Kh\u00f3a ch\u00ednh\" width=\"800\" height=\"500\" class=\"size-full wp-image-28925\" title=\"\" srcset=\"https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Loi-ich-cua-Khoa-chinh-2.jpg 800w, https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Loi-ich-cua-Khoa-chinh-2-300x188.jpg 300w, https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Loi-ich-cua-Khoa-chinh-2-768x480.jpg 768w, https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Loi-ich-cua-Khoa-chinh-2-750x469.jpg 750w\" sizes=\"auto, (max-width: 800px) 100vw, 800px\" \/><figcaption id=\"caption-attachment-28925\" class=\"wp-caption-text\">L\u1ee3i \u00edch c\u1ee7a Kh\u00f3a ch\u00ednh<\/figcaption><\/figure>\n<h3><span class=\"ez-toc-section\" id=\"Don-gian-hoa-viec-thiet-lap-moi-quan-he\"><\/span>\u0110\u01a1n gi\u1ea3n h\u00f3a vi\u1ec7c thi\u1ebft l\u1eadp m\u1ed1i quan h\u1ec7<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Kh\u00f3a ch\u00ednh \u0111\u00f3ng vai tr\u00f2 l\u00e0 <strong>&#8220;\u0111i\u1ec3m tham chi\u1ebfu&#8221; r\u00f5 r\u00e0ng v\u00e0 \u0111\u00e1ng tin c\u1eady cho Kh\u00f3a ngo\u1ea1i<\/strong> (Foreign Key) \u1edf c\u00e1c b\u1ea3ng kh\u00e1c. N\u00f3 gi\u00fap b\u1ea1n d\u1ec5 d\u00e0ng \u0111\u1ecbnh ngh\u0129a v\u00e0 qu\u1ea3n l\u00fd c\u00e1c m\u1ed1i quan h\u1ec7 gi\u1eefa c\u00e1c b\u1ea3ng trong c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 (Relationship Management), \u0111\u1ea3m b\u1ea3o c\u00e1c li\u00ean k\u1ebft d\u1eef li\u1ec7u lu\u00f4n ch\u00ednh x\u00e1c v\u00e0 h\u1ee3p l\u00fd.<\/p>\n<p>Vi\u1ec7c n\u00e0y \u0111\u01a1n gi\u1ea3n h\u00f3a \u0111\u00e1ng k\u1ec3 qu\u00e1 tr\u00ecnh thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 gi\u00fap b\u1ea1n x\u00e2y d\u1ef1ng c\u00e1c m\u00f4 h\u00ecnh d\u1eef li\u1ec7u ph\u1ee9c t\u1ea1p nh\u01b0ng v\u1eabn c\u00f3 c\u1ea5u tr\u00fac ch\u1eb7t ch\u1ebd. M\u1ed1i quan h\u1ec7 gi\u1eefa c\u00e1c b\u1ea3ng tr\u1edf n\u00ean minh b\u1ea1ch v\u00e0 d\u1ec5 theo d\u00f5i h\u01a1n r\u1ea5t nhi\u1ec1u nh\u1edd c\u00f3 Kh\u00f3a ch\u00ednh.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Ho-tro-thao-tac-du-lieu-Cap-nhatXoa\"><\/span>H\u1ed7 tr\u1ee3 thao t\u00e1c d\u1eef li\u1ec7u (C\u1eadp nh\u1eadt\/X\u00f3a)<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Khi b\u1ea1n c\u1ea7n th\u1ef1c hi\u1ec7n c\u00e1c thao t\u00e1c ch\u1ec9nh s\u1eeda (UPDATE) ho\u1eb7c x\u00f3a (DELETE) m\u1ed9t b\u1ea3n ghi c\u1ee5 th\u1ec3, Kh\u00f3a ch\u00ednh cung c\u1ea5p m\u1ed9t c\u00e1ch th\u1ee9c ch\u00ednh x\u00e1c \u0111\u1ec3 ch\u1ec9 \u0111\u1ecbnh b\u1ea3n ghi \u0111\u00f3. B\u1ea1n ch\u1ec9 c\u1ea7n cung c\u1ea5p gi\u00e1 tr\u1ecb Kh\u00f3a ch\u00ednh c\u1ee7a b\u1ea3n ghi m\u1ee5c ti\u00eau, \u0111\u1ea3m b\u1ea3o r\u1eb1ng ch\u1ec9 b\u1ea3n ghi mong mu\u1ed1n b\u1ecb t\u00e1c \u0111\u1ed9ng m\u00e0 kh\u00f4ng \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn b\u1ea5t k\u1ef3 d\u1eef li\u1ec7u n\u00e0o kh\u00e1c trong b\u1ea3ng.<\/p>\n<p>\u0110i\u1ec1u n\u00e0y gi\u1ea3m thi\u1ec3u r\u1ee7i ro x\u00f3a nh\u1ea7m ho\u1eb7c c\u1eadp nh\u1eadt sai d\u1eef li\u1ec7u, \u0111\u1eb7c bi\u1ec7t quan tr\u1ecdng trong c\u00e1c h\u1ec7 th\u1ed1ng c\u00f3 s\u1ed1 l\u01b0\u1ee3ng b\u1ea3n ghi l\u1edbn ho\u1eb7c c\u00e1c thao t\u00e1c mang t\u00ednh nh\u1ea1y c\u1ea3m cao.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Nen-tang-cho-thiet-ke-CSDL-tot\"><\/span>N\u1ec1n t\u1ea3ng cho thi\u1ebft k\u1ebf CSDL t\u1ed1t<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Vi\u1ec7c s\u1eed d\u1ee5ng Kh\u00f3a ch\u00ednh m\u1ed9t c\u00e1ch nh\u1ea5t qu\u00e1n v\u00e0 chu\u1ea9n x\u00e1c l\u00e0<strong> n\u1ec1n t\u1ea3ng kh\u00f4ng th\u1ec3 thi\u1ebfu<\/strong> cho m\u1ed9t thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u t\u1ed1t v\u00e0 hi\u1ec7u qu\u1ea3. N\u00f3 gi\u00fap t\u1ed5 ch\u1ee9c d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch logic, d\u1ec5 hi\u1ec3u, gi\u1ea3m thi\u1ec3u s\u1ef1 d\u01b0 th\u1eeba th\u00f4ng tin v\u00e0 h\u1ed7 tr\u1ee3 qu\u00e1 tr\u00ecnh chu\u1ea9n h\u00f3a (Normalization), t\u1eeb \u0111\u00f3 gi\u00fap h\u1ec7 th\u1ed1ng d\u1ec5 ph\u00e1t tri\u1ec3n, m\u1edf r\u1ed9ng v\u00e0 b\u1ea3o tr\u00ec v\u1ec1 l\u00e2u d\u00e0i.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Su-khac-biet-giua-Khoa-chinh-va-Khoa-ngoai\"><\/span>S\u1ef1 kh\u00e1c bi\u1ec7t gi\u1eefa Kh\u00f3a ch\u00ednh v\u00e0 Kh\u00f3a ngo\u1ea1i<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>S\u1ef1 nh\u1ea7m l\u1eabn gi\u1eefa Kh\u00f3a ch\u00ednh (Primary Key) v\u00e0 Kh\u00f3a ngo\u1ea1i (Foreign Key) l\u00e0 \u0111i\u1ec1u kh\u00e1 ph\u1ed5 bi\u1ebfn khi m\u1edbi b\u1eaft \u0111\u1ea7u l\u00e0m quen v\u1edbi c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7. \u0110i\u1ec3m kh\u00e1c bi\u1ec7t c\u01a1 b\u1ea3n nh\u1ea5t n\u1eb1m \u1edf vai tr\u00f2 v\u00e0 m\u1ee5c \u0111\u00edch s\u1eed d\u1ee5ng c\u1ee7a ch\u00fang: Kh\u00f3a ch\u00ednh d\u00f9ng \u0111\u1ec3 <strong>\u0111\u1ecbnh danh duy nh\u1ea5t<\/strong> c\u00e1c b\u1ea3n ghi trong <em>ch\u00ednh b\u1ea3ng ch\u1ee9a n\u00f3<\/em>, c\u00f2n Kh\u00f3a ngo\u1ea1i d\u00f9ng \u0111\u1ec3 <strong>li\u00ean k\u1ebft<\/strong> c\u00e1c b\u1ea3n ghi gi\u1eefa hai b\u1ea3ng kh\u00e1c nhau b\u1eb1ng c\u00e1ch <em>tham chi\u1ebfu<\/em> \u0111\u1ebfn Kh\u00f3a ch\u00ednh (ho\u1eb7c Kh\u00f3a \u1ee9ng vi\u00ean) \u1edf b\u1ea3ng kia.<\/p>\n<p>Vi\u1ec7c hi\u1ec3u r\u00f5 s\u1ef1 kh\u00e1c bi\u1ec7t n\u00e0y l\u00e0 n\u1ec1n t\u1ea3ng \u0111\u1ec3 b\u1ea1n c\u00f3 th\u1ec3 thi\u1ebft k\u1ebf v\u00e0 qu\u1ea3n l\u00fd c\u1ea5u tr\u00fac c\u01a1 s\u1edf d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch ch\u00ednh x\u00e1c, \u0111\u1ea3m b\u1ea3o c\u00e1c m\u1ed1i quan h\u1ec7 gi\u1eefa d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c \u0111\u1ecbnh ngh\u0129a \u0111\u00fang \u0111\u1eafn.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Muc-dich-va-Vai-tro\"><\/span>M\u1ee5c \u0111\u00edch v\u00e0 Vai tr\u00f2<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>M\u1ee5c \u0111\u00edch ch\u00ednh c\u1ee7a Kh\u00f3a ch\u00ednh l\u00e0 cung c\u1ea5p m\u1ed9t &#8220;danh t\u00ednh&#8221; duy nh\u1ea5t v\u00e0 kh\u00f4ng th\u1ec3 tr\u00f9ng l\u1eb7p cho m\u1ed7i d\u00f2ng d\u1eef li\u1ec7u (b\u1ea3n ghi) trong b\u1ea3ng. N\u00f3 \u0111\u1ea3m b\u1ea3o r\u1eb1ng m\u1ed7i b\u1ea3n ghi c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh m\u1ed9t c\u00e1ch ri\u00eang bi\u1ec7t v\u00e0 duy nh\u1ea5t, \u0111\u1ed3ng th\u1eddi th\u1ef1c thi t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u b\u1eb1ng c\u00e1ch ng\u0103n ch\u1eb7n s\u1ef1 tr\u00f9ng l\u1eb7p v\u00e0 gi\u00e1 tr\u1ecb r\u1ed7ng.<\/p>\n<p>Ng\u01b0\u1ee3c l\u1ea1i, m\u1ee5c \u0111\u00edch ch\u00ednh c\u1ee7a Kh\u00f3a ngo\u1ea1i l\u00e0 thi\u1ebft l\u1eadp v\u00e0 duy tr\u00ec m\u1ed1i li\u00ean k\u1ebft logic gi\u1eefa hai b\u1ea3ng. N\u00f3 ho\u1ea1t \u0111\u1ed9ng nh\u01b0 m\u1ed9t &#8220;c\u1ea7u n\u1ed1i&#8221;, cho ph\u00e9p d\u1eef li\u1ec7u t\u1eeb m\u1ed9t b\u1ea3ng tham chi\u1ebfu \u0111\u1ebfn d\u1eef li\u1ec7u \u1edf m\u1ed9t b\u1ea3ng kh\u00e1c, t\u1eeb \u0111\u00f3 \u0111\u1ea3m b\u1ea3o t\u00ednh to\u00e0n v\u1eb9n tham chi\u1ebfu gi\u1eefa ch\u00fang.<\/p>\n<figure id=\"attachment_28924\" aria-describedby=\"caption-attachment-28924\" style=\"width: 800px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Su-khac-biet-giua-Khoa-chinh-va-Khoa-ngoai-2.jpg\" alt=\" S\u1ef1 kh\u00e1c bi\u1ec7t gi\u1eefa Kh\u00f3a ch\u00ednh v\u00e0 Kh\u00f3a ngo\u1ea1i\" width=\"800\" height=\"500\" class=\"size-full wp-image-28924\" title=\"\" srcset=\"https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Su-khac-biet-giua-Khoa-chinh-va-Khoa-ngoai-2.jpg 800w, https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Su-khac-biet-giua-Khoa-chinh-va-Khoa-ngoai-2-300x188.jpg 300w, https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Su-khac-biet-giua-Khoa-chinh-va-Khoa-ngoai-2-768x480.jpg 768w, https:\/\/interdata.vn\/blog\/wp-content\/uploads\/2025\/05\/Su-khac-biet-giua-Khoa-chinh-va-Khoa-ngoai-2-750x469.jpg 750w\" sizes=\"auto, (max-width: 800px) 100vw, 800px\" \/><figcaption id=\"caption-attachment-28924\" class=\"wp-caption-text\">S\u1ef1 kh\u00e1c bi\u1ec7t gi\u1eefa Kh\u00f3a ch\u00ednh v\u00e0 Kh\u00f3a ngo\u1ea1i<\/figcaption><\/figure>\n<h3><span class=\"ez-toc-section\" id=\"Dac-diem\"><\/span>\u0110\u1eb7c \u0111i\u1ec3m<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Kh\u00f3a ch\u00ednh c\u00f3 hai \u0111\u1eb7c \u0111i\u1ec3m b\u1eaft bu\u1ed9c v\u00e0 kh\u00f4ng th\u1ec3 thay \u0111\u1ed5i: n\u00f3 ph\u1ea3i l\u00e0 <strong>Duy nh\u1ea5t (Unique)<\/strong> v\u00e0 <strong>Kh\u00f4ng r\u1ed7ng (Not Null)<\/strong>. Ngh\u0129a l\u00e0, m\u1ed7i gi\u00e1 tr\u1ecb Kh\u00f3a ch\u00ednh ch\u1ec9 xu\u1ea5t hi\u1ec7n m\u1ed9t l\u1ea7n duy nh\u1ea5t trong b\u1ea3ng v\u00e0 kh\u00f4ng bao gi\u1edd \u0111\u01b0\u1ee3c \u0111\u1ec3 tr\u1ed1ng.<\/p>\n<p>Trong khi \u0111\u00f3, Kh\u00f3a ngo\u1ea1i c\u00f3 th\u1ec3 c\u00f3 <strong>gi\u00e1 tr\u1ecb tr\u00f9ng l\u1eb7p trong c\u1ed9t Kh\u00f3a ngo\u1ea1i \u1edf b\u1ea3ng ch\u1ee9a n\u00f3<\/strong>. \u0110i\u1ec1u n\u00e0y ho\u00e0n to\u00e0n b\u00ecnh th\u01b0\u1eddng v\u00ec nhi\u1ec1u b\u1ea3n ghi \u1edf b\u1ea3ng &#8220;con&#8221; c\u00f3 th\u1ec3 c\u00f9ng li\u00ean k\u1ebft \u0111\u1ebfn m\u1ed9t b\u1ea3n ghi duy nh\u1ea5t \u1edf b\u1ea3ng &#8220;cha&#8221; (b\u1ea3ng ch\u1ee9a Kh\u00f3a ch\u00ednh). T\u00f9y c\u1ea5u h\u00ecnh, Kh\u00f3a ngo\u1ea1i <strong>c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c ph\u00e9p r\u1ed7ng (NULL)<\/strong> n\u1ebfu m\u1ed1i quan h\u1ec7 cho ph\u00e9p b\u1ea3n ghi \u1edf b\u1ea3ng con kh\u00f4ng nh\u1ea5t thi\u1ebft ph\u1ea3i li\u00ean k\u1ebft v\u1edbi b\u1ea5t k\u1ef3 b\u1ea3n ghi n\u00e0o \u1edf b\u1ea3ng cha.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"So-luong-trong-Bang\"><\/span>S\u1ed1 l\u01b0\u1ee3ng trong B\u1ea3ng<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Theo quy t\u1eafc thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7, m\u1ed7i b\u1ea3ng ch\u1ec9 \u0111\u01b0\u1ee3c ph\u00e9p c\u00f3 <strong>duy nh\u1ea5t m\u1ed9t Kh\u00f3a ch\u00ednh<\/strong>. Kh\u00f3a ch\u00ednh n\u00e0y c\u00f3 th\u1ec3 l\u00e0 m\u1ed9t c\u1ed9t \u0111\u01a1n ho\u1eb7c l\u00e0 s\u1ef1 k\u1ebft h\u1ee3p c\u1ee7a nhi\u1ec1u c\u1ed9t (Kh\u00f3a ch\u00ednh k\u1ebft h\u1ee3p), nh\u01b0ng ch\u00fang c\u00f9ng nhau t\u1ea1o n\u00ean ch\u1ec9 m\u1ed9t Kh\u00f3a ch\u00ednh duy nh\u1ea5t cho to\u00e0n b\u1ed9 b\u1ea3ng.<\/p>\n<p>M\u1eb7t kh\u00e1c, m\u1ed9t b\u1ea3ng c\u00f3 th\u1ec3 ch\u1ee9a <strong>nhi\u1ec1u Kh\u00f3a ngo\u1ea1i<\/strong>. \u0110i\u1ec1u n\u00e0y x\u1ea3y ra khi b\u1ea3ng \u0111\u00f3 c\u1ea7n thi\u1ebft l\u1eadp m\u1ed1i li\u00ean k\u1ebft v\u1edbi nhi\u1ec1u b\u1ea3ng kh\u00e1c nhau trong c\u01a1 s\u1edf d\u1eef li\u1ec7u. M\u1ed7i Kh\u00f3a ngo\u1ea1i s\u1ebd \u0111\u1ea1i di\u1ec7n cho m\u1ed9t m\u1ed1i quan h\u1ec7 ri\u00eang bi\u1ec7t \u0111\u1ebfn m\u1ed9t b\u1ea3ng &#8220;cha&#8221; kh\u00e1c.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Vi-du-minh-hoa\"><\/span>V\u00ed d\u1ee5 minh h\u1ecda<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>H\u00e3y xem x\u00e9t hai b\u1ea3ng ph\u1ed5 bi\u1ebfn: <code>KHACH_HANG<\/code> v\u00e0 <code>DON_HANG<\/code>. B\u1ea3ng <code>KHACH_HANG<\/code> l\u01b0u th\u00f4ng tin v\u1ec1 kh\u00e1ch h\u00e0ng, c\u00f2n b\u1ea3ng <code>DON_HANG<\/code> l\u01b0u th\u00f4ng tin v\u1ec1 c\u00e1c \u0111\u01a1n \u0111\u1eb7t h\u00e0ng.<\/p>\n<p>Trong b\u1ea3ng <code>KHACH_HANG<\/code>, c\u1ed9t <code>MaKH<\/code> (M\u00e3 Kh\u00e1ch h\u00e0ng) \u0111\u00f3ng vai tr\u00f2 l\u00e0 <strong>Kh\u00f3a ch\u00ednh<\/strong>. M\u1ed7i gi\u00e1 tr\u1ecb <code>MaKH<\/code> l\u00e0 duy nh\u1ea5t cho m\u1ed7i kh\u00e1ch h\u00e0ng v\u00e0 kh\u00f4ng \u0111\u01b0\u1ee3c r\u1ed7ng, gi\u00fap ph\u00e2n bi\u1ec7t c\u00e1c kh\u00e1ch h\u00e0ng ri\u00eang l\u1ebb.<\/p>\n<p>Trong b\u1ea3ng <code>DON_HANG<\/code>, ch\u00fang ta c\u1ea7n bi\u1ebft \u0111\u01a1n h\u00e0ng n\u00e0y do kh\u00e1ch h\u00e0ng n\u00e0o \u0111\u1eb7t. C\u1ed9t <code>MaKH<\/code> trong b\u1ea3ng <code>DON_HANG<\/code> \u0111\u00f3ng vai tr\u00f2 l\u00e0 <strong>Kh\u00f3a ngo\u1ea1i<\/strong>. Gi\u00e1 tr\u1ecb c\u1ee7a c\u1ed9t <code>MaKH<\/code> \u1edf \u0111\u00e2y s\u1ebd <em>tham chi\u1ebfu<\/em> \u0111\u1ebfn gi\u00e1 tr\u1ecb <code>MaKH<\/code> (Kh\u00f3a ch\u00ednh) \u1edf b\u1ea3ng <code>KHACH_HANG<\/code>, thi\u1ebft l\u1eadp m\u1ed1i li\u00ean k\u1ebft &#8220;m\u1ed9t kh\u00e1ch h\u00e0ng c\u00f3 th\u1ec3 c\u00f3 nhi\u1ec1u \u0111\u01a1n h\u00e0ng&#8221;.<\/p>\n<p>M\u1ed9t \u0111i\u1ec3m kh\u00e1c bi\u1ec7t r\u00f5 r\u00e0ng qua v\u00ed d\u1ee5: <code>MaKH<\/code> trong b\u1ea3ng <code>KHACH_HANG<\/code> l\u00e0 duy nh\u1ea5t, nh\u01b0ng <code>MaKH<\/code> trong b\u1ea3ng <code>DON_HANG<\/code> c\u00f3 th\u1ec3 l\u1eb7p l\u1ea1i (v\u00ec m\u1ed9t kh\u00e1ch h\u00e0ng c\u00f3 th\u1ec3 \u0111\u1eb7t nhi\u1ec1u \u0111\u01a1n h\u00e0ng).<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Cau-hoi-thuong-gap-ve-Khoa-chinh-Primary-Key\"><\/span>C\u00e2u h\u1ecfi th\u01b0\u1eddng g\u1eb7p v\u1ec1 Kh\u00f3a ch\u00ednh (Primary Key)<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><span class=\"ez-toc-section\" id=\"Mot-bang-trong-co-so-du-lieu-co-the-co-bao-nhieu-Khoa-chinh\"><\/span>M\u1ed9t b\u1ea3ng trong c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u00f3 th\u1ec3 c\u00f3 bao nhi\u00eau Kh\u00f3a ch\u00ednh?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Theo nguy\u00ean t\u1eafc c\u1ee7a m\u00f4 h\u00ecnh c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 chu\u1ea9n, m\u1ed7i b\u1ea3ng ch\u1ec9 \u0111\u01b0\u1ee3c ph\u00e9p c\u00f3 duy nh\u1ea5t m\u1ed9t Kh\u00f3a ch\u00ednh. Kh\u00f3a ch\u00ednh n\u00e0y c\u00f3 th\u1ec3 l\u00e0 m\u1ed9t c\u1ed9t \u0111\u01a1n ho\u1eb7c l\u00e0 t\u1ed5 h\u1ee3p c\u1ee7a nhi\u1ec1u c\u1ed9t.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Khoa-chinh-co-phai-la-chi-muc-Index-khong\"><\/span>Kh\u00f3a ch\u00ednh c\u00f3 ph\u1ea3i l\u00e0 ch\u1ec9 m\u1ee5c (Index) kh\u00f4ng?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Kh\u00f3a ch\u00ednh kh\u00f4ng ph\u1ea3i l\u00e0 ch\u1ec9 m\u1ee5c, nh\u01b0ng h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u (DBMS) th\u01b0\u1eddng t\u1ef1 \u0111\u1ed9ng t\u1ea1o m\u1ed9t ch\u1ec9 m\u1ee5c tr\u00ean c\u1ed9t Kh\u00f3a ch\u00ednh. Ch\u1ec9 m\u1ee5c n\u00e0y gi\u00fap th\u1ef1c thi t\u00ednh duy nh\u1ea5t v\u00e0 t\u0103ng t\u1ed1c \u0111\u1ed9 t\u00ecm ki\u1ebfm\/truy xu\u1ea5t b\u1ea3n ghi d\u1ef1a tr\u00ean gi\u00e1 tr\u1ecb Kh\u00f3a ch\u00ednh.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Lam-the-nao-de-chon-Khoa-chinh-phu-hop-nhat-cho-mot-bang-du-lieu\"><\/span>L\u00e0m th\u1ebf n\u00e0o \u0111\u1ec3 ch\u1ecdn Kh\u00f3a ch\u00ednh ph\u00f9 h\u1ee3p nh\u1ea5t cho m\u1ed9t b\u1ea3ng d\u1eef li\u1ec7u?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Ch\u1ecdn Kh\u00f3a ch\u00ednh c\u1ea7n \u0111\u1ea3m b\u1ea3o c\u00e1c ti\u00eau ch\u00ed: lu\u00f4n duy nh\u1ea5t, kh\u00f4ng bao gi\u1edd r\u1ed7ng, gi\u00e1 tr\u1ecb \u1ed5n \u0111\u1ecbnh (\u00edt thay \u0111\u1ed5i), v\u00e0 l\u00fd t\u01b0\u1edfng l\u00e0 \u0111\u01a1n gi\u1ea3n, kh\u00f4ng mang \u00fd ngh\u0129a nghi\u1ec7p v\u1ee5 c\u00f3 th\u1ec3 thay \u0111\u1ed5i. M\u00e3 \u0111\u1ecbnh danh t\u1ef1 t\u0103ng (Auto Increment ID) th\u01b0\u1eddng l\u00e0 l\u1ef1a ch\u1ecdn t\u1ed1t.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Su-khac-nhau-giua-Khoa-chinh-va-Khoa-ung-vien-Candidate-Key-la-gi\"><\/span>S\u1ef1 kh\u00e1c nhau gi\u1eefa Kh\u00f3a ch\u00ednh v\u00e0 Kh\u00f3a \u1ee9ng vi\u00ean (Candidate Key) l\u00e0 g\u00ec?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Kh\u00f3a \u1ee9ng vi\u00ean l\u00e0 b\u1ea5t k\u1ef3 t\u1eadp h\u1ee3p c\u1ed9t t\u1ed1i thi\u1ec3u n\u00e0o c\u00f3 th\u1ec3 \u0111\u1ecbnh danh duy nh\u1ea5t b\u1ea3n ghi. M\u1ed9t b\u1ea3ng c\u00f3 th\u1ec3 c\u00f3 nhi\u1ec1u Kh\u00f3a \u1ee9ng vi\u00ean. Kh\u00f3a ch\u00ednh l\u00e0 Kh\u00f3a \u1ee9ng vi\u00ean \u0111\u01b0\u1ee3c l\u1ef1a ch\u1ecdn \u0111\u1ec3 l\u00e0m \u0111\u1ecbnh danh ch\u00ednh th\u1ee9c v\u00e0 duy nh\u1ea5t cho b\u1ea3ng \u0111\u00f3.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Dieu-gi-se-xay-ra-voi-du-lieu-va-cau-truc-neu-mot-bang-khong-co-Khoa-chinh\"><\/span>\u0110i\u1ec1u g\u00ec s\u1ebd x\u1ea3y ra v\u1edbi d\u1eef li\u1ec7u v\u00e0 c\u1ea5u tr\u00fac n\u1ebfu m\u1ed9t b\u1ea3ng kh\u00f4ng c\u00f3 Kh\u00f3a ch\u00ednh?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>N\u1ebfu m\u1ed9t b\u1ea3ng kh\u00f4ng c\u00f3 Kh\u00f3a ch\u00ednh, b\u1ea1n s\u1ebd g\u1eb7p kh\u00f3 kh\u0103n l\u1edbn trong vi\u1ec7c \u0111\u1ea3m b\u1ea3o t\u00ednh duy nh\u1ea5t c\u1ee7a d\u1eef li\u1ec7u (c\u00f3 th\u1ec3 ch\u00e8n b\u1ea3n ghi tr\u00f9ng l\u1eb7p), kh\u00f4ng th\u1ec3 thi\u1ebft l\u1eadp m\u1ed1i quan h\u1ec7 r\u00e0ng bu\u1ed9c v\u1edbi c\u00e1c b\u1ea3ng kh\u00e1c, v\u00e0 vi\u1ec7c truy xu\u1ea5t\/c\u1eadp nh\u1eadt\/x\u00f3a b\u1ea3n ghi c\u1ee5 th\u1ec3 tr\u1edf n\u00ean ph\u1ee9c t\u1ea1p v\u00e0 k\u00e9m hi\u1ec7u qu\u1ea3.<\/p>\n<p>Hi\u1ec3u r\u00f5 <strong>Kh\u00f3a ch\u00ednh l\u00e0 g\u00ec<\/strong> v\u00e0 s\u1eed d\u1ee5ng \u0111\u00fang c\u00e1ch s\u1ebd gi\u00fap b\u1ea1n thi\u1ebft k\u1ebf c\u01a1 s\u1edf d\u1eef li\u1ec7u ch\u1eb7t ch\u1ebd, d\u1ec5 b\u1ea3o tr\u00ec v\u00e0 hi\u1ec7u qu\u1ea3 l\u00e2u d\u00e0i. T\u1eeb vi\u1ec7c \u0111\u1ecbnh danh duy nh\u1ea5t b\u1ea3n ghi \u0111\u1ebfn h\u1ed7 tr\u1ee3 c\u00e1c truy v\u1ea5n t\u1ed1i \u01b0u, kh\u00f3a ch\u00ednh \u0111\u00f3ng vai tr\u00f2 kh\u00f4ng th\u1ec3 thi\u1ebfu trong b\u1ea5t k\u1ef3 h\u1ec7 qu\u1ea3n tr\u1ecb d\u1eef li\u1ec7u n\u00e0o. N\u1ebfu b\u1ea1n \u0111ang x\u00e2y d\u1ef1ng ho\u1eb7c t\u1ed1i \u01b0u h\u1ec7 th\u1ed1ng d\u1eef li\u1ec7u, \u0111\u1eebng b\u1ecf qua vi\u1ec7c khai th\u00e1c tri\u1ec7t \u0111\u1ec3 s\u1ee9c m\u1ea1nh c\u1ee7a kh\u00f3a ch\u00ednh.<\/p>\n<p>\u0110\u1eebng qu\u00ean theo d\u00f5i <strong><a href=\"https:\/\/interdata.vn\/\">InterData<\/a> <\/strong>\u0111\u1ec3 c\u1eadp nh\u1eadt th\u00eam nhi\u1ec1u ki\u1ebfn th\u1ee9c th\u1ef1c ti\u1ec5n v\u1ec1 c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 l\u1eadp tr\u00ecnh \u1ee9ng d\u1ee5ng.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Trong c\u01a1 s\u1edf d\u1eef li\u1ec7u, Kh\u00f3a ch\u00ednh (Primary Key) l\u00e0 n\u1ec1n t\u1ea3ng quan tr\u1ecdng gi\u00fap x\u00e1c \u0111\u1ecbnh, qu\u1ea3n l\u00fd v\u00e0 truy xu\u1ea5t th\u00f4ng tin m\u1ed9t c\u00e1ch ch\u00ednh x\u00e1c. Kh\u00f4ng ch\u1ec9 \u0111\u1ea3m b\u1ea3o t\u00ednh duy nh\u1ea5t cho m\u1ed7i b\u1ea3n ghi, kh\u00f3a ch\u00ednh c\u00f2n \u0111\u00f3ng vai tr\u00f2 then ch\u1ed1t trong vi\u1ec7c duy tr\u00ec to\u00e0n v\u1eb9n d\u1eef li\u1ec7u<\/p>\n","protected":false},"author":11,"featured_media":28465,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[140],"tags":[],"class_list":["post-28439","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-lap-trinh"],"_links":{"self":[{"href":"https:\/\/interdata.vn\/blog\/wp-json\/wp\/v2\/posts\/28439","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/interdata.vn\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/interdata.vn\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/interdata.vn\/blog\/wp-json\/wp\/v2\/users\/11"}],"replies":[{"embeddable":true,"href":"https:\/\/interdata.vn\/blog\/wp-json\/wp\/v2\/comments?post=28439"}],"version-history":[{"count":4,"href":"https:\/\/interdata.vn\/blog\/wp-json\/wp\/v2\/posts\/28439\/revisions"}],"predecessor-version":[{"id":28929,"href":"https:\/\/interdata.vn\/blog\/wp-json\/wp\/v2\/posts\/28439\/revisions\/28929"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/interdata.vn\/blog\/wp-json\/wp\/v2\/media\/28465"}],"wp:attachment":[{"href":"https:\/\/interdata.vn\/blog\/wp-json\/wp\/v2\/media?parent=28439"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/interdata.vn\/blog\/wp-json\/wp\/v2\/categories?post=28439"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/interdata.vn\/blog\/wp-json\/wp\/v2\/tags?post=28439"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}