{"id":5436,"date":"2021-12-26T22:25:24","date_gmt":"2021-12-26T15:25:24","guid":{"rendered":"https:\/\/webvocuc.com\/blog\/?p=5436"},"modified":"2021-12-09T23:02:01","modified_gmt":"2021-12-09T16:02:01","slug":"co-so-du-lieu-quan-he-la-gi-tam-quan-trong","status":"publish","type":"post","link":"https:\/\/webvocuc.com\/blog\/co-so-du-lieu-quan-he-la-gi-tam-quan-trong.html","title":{"rendered":"C\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 l\u00e0 g\u00ec? T\u1ea7m quan tr\u1ecdng c\u1ee7a n\u00f3"},"content":{"rendered":"<p><a href=\"https:\/\/webvocuc.com\/blog\/?p=5436&amp;preview=true\" target=\"_blank\" rel=\"noopener\"><strong>C\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7<\/strong><\/a> l\u00e0 g\u00ec? M\u1ee5c \u0111\u00edch c\u1ee7a c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 l\u00e0 \u0111em \u0111\u1ebfn t\u00ednh hi\u1ec7u qu\u1ea3 cho t\u1ed5 ch\u1ee9c v\u00e0 t\u00ednh ch\u00ednh x\u00e1c c\u1ee7a n\u00f3.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-5469 size-full aligncenter\" src=\"https:\/\/webvocuc.com\/blog\/wp-content\/uploads\/2021\/12\/dbms-la-gi.jpg\" alt=\"co-so-du-lieu-quan-he-la-gi-tam-quan-trong\" width=\"576\" height=\"324\" title=\"\" srcset=\"https:\/\/webvocuc.com\/blog\/wp-content\/uploads\/2021\/12\/dbms-la-gi.jpg 576w, https:\/\/webvocuc.com\/blog\/wp-content\/uploads\/2021\/12\/dbms-la-gi-300x169.jpg 300w, https:\/\/webvocuc.com\/blog\/wp-content\/uploads\/2021\/12\/dbms-la-gi-525x295.jpg 525w\" sizes=\"auto, (max-width: 576px) 100vw, 576px\" \/><\/p>\n<h2 id=\"ftoc-heading-3\" class=\"ftwp-heading\"><b>Kh\u00e1i ni\u1ec7m c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7\u00a0<\/b><\/h2>\n<p>Ch\u00fang ta c\u00f3 th\u1ec3 n\u1eafm b\u1eaft \u0111\u01b0\u1ee3c kh\u00e1i ni\u1ec7m\u00a0<b>c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 l\u00e0 g\u00ec\u00a0<\/b>theo m\u1ed9t c\u00e1ch \u0111\u01a1n gi\u1ea3n nh\u1ea5t \u0111\u00f3 l\u00e0 s\u1ef1 t\u1eadp h\u1ee3p c\u1ee7a c\u00e1c t\u1ed5 ch\u1ee9c theo b\u1ea3ng. B\u00ean c\u1ea1nh \u0111\u00f3, ch\u00fang \u0111\u1ec1u c\u00f3 m\u1ed9t m\u1ed1i quan h\u1ec7 m\u1eadt thi\u1ebft v\u1edbi nhau \u0111\u1ec3 gi\u1ea3m thi\u1ec3u s\u1ef1 d\u01b0 th\u1eeba c\u1ee7a d\u1eef li\u1ec7u.<\/p>\n<p>M\u1eb7t kh\u00e1c, c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 n\u00e0y v\u1eabn \u0111\u1ea3m b\u1ea3o \u0111\u01b0\u1ee3c t\u00ednh hi\u1ec7u qu\u1ea3 trong vi\u1ec7c l\u01b0u tr\u1eef v\u00e0 truy xu\u1ea5t c\u00e1c d\u1eef li\u1ec7u. Hi\u1ec7n nay, ch\u00fang ta th\u01b0\u1eddng th\u1ea5y c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 \u0111\u01b0\u1ee3c xu\u1ea5t hi\u1ec7n nhi\u1ec1u nh\u1ea5t trong c\u00e1c h\u1ec7 th\u1ed1ng ph\u1ea7n m\u1ec1m t\u1eeb c\u00e1c doanh nghi\u1ec7p c\u1ee7a nhi\u1ec1u v\u1ecb tr\u00ed kh\u00e1c nhau ho\u1eb7c l\u00e0 trong c\u00e1c ng\u00e2n h\u00e0ng. T\u1ea5t c\u1ea3 \u0111\u1ec1u nh\u1eb1m \u0111\u1ebfn m\u1ee5c \u0111\u00edch l\u00e0 \u0111em t\u00ednh hi\u1ec7u qu\u1ea3 c\u1ee7a t\u1ed5 ch\u1ee9c v\u00e0 t\u00ednh ch\u00ednh x\u00e1c c\u1ee7a n\u00f3.<\/p>\n<h2 id=\"ftoc-heading-4\" class=\"ftwp-heading\"><b>Th\u00e0nh ph\u1ea7n c\u01a1 b\u1ea3n xu\u1ea5t hi\u1ec7n trong c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7<\/b><\/h2>\n<p>\u0110\u1ec3 c\u00f3 th\u1ec3 t\u1ea1o n\u00ean m\u1ed9t c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 th\u00e0nh c\u00f4ng ch\u00fang ta kh\u00f4ng th\u1ec3 thi\u1ebfu \u0111i s\u1ef1 xu\u1ea5t hi\u1ec7n c\u1ee7a c\u00e1c th\u00e0nh ph\u1ea7n c\u01a1 b\u1ea3n:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-5468 size-full aligncenter\" src=\"https:\/\/webvocuc.com\/blog\/wp-content\/uploads\/2021\/12\/he-quan-tri-co-so-du-lieu-la-gi.jpg\" alt=\"co-so-du-lieu-quan-he-la-gi-tam-quan-trong\" width=\"800\" height=\"400\" title=\"\" srcset=\"https:\/\/webvocuc.com\/blog\/wp-content\/uploads\/2021\/12\/he-quan-tri-co-so-du-lieu-la-gi.jpg 800w, https:\/\/webvocuc.com\/blog\/wp-content\/uploads\/2021\/12\/he-quan-tri-co-so-du-lieu-la-gi-300x150.jpg 300w, https:\/\/webvocuc.com\/blog\/wp-content\/uploads\/2021\/12\/he-quan-tri-co-so-du-lieu-la-gi-768x384.jpg 768w, https:\/\/webvocuc.com\/blog\/wp-content\/uploads\/2021\/12\/he-quan-tri-co-so-du-lieu-la-gi-525x263.jpg 525w\" sizes=\"auto, (max-width: 800px) 100vw, 800px\" \/><\/p>\n<h3 id=\"ftoc-heading-5\" class=\"ftwp-heading\"><b>B\u1ea3ng ch\u1ee9a d\u1eef li\u1ec7u<\/b><\/h3>\n<p>M\u1ed9t trong nh\u1eefng y\u1ebfu t\u1ed1 quan tr\u1ecdng m\u00e0 ch\u00fang ta kh\u00f4ng th\u1ec3 kh\u00f4ng nh\u1eafc \u0111\u1ebfn \u0111\u00f3 ch\u00ednh l\u00e0 b\u1ea3ng ch\u1ee9a d\u1eef li\u1ec7u. Trong \u0111\u00f3, n\u00f3 c\u00f3 ch\u1ee9a c\u00e1c th\u00e0nh ph\u1ea7n:<\/p>\n<ul>\n<li aria-level=\"1\">D\u00f2ng: hay c\u00f2n c\u00f3 th\u1ec3 g\u1ecdi l\u00e0 row, \u0111\u00e2y l\u00e0 d\u00f2ng d\u1eef li\u1ec7u trong \u0111\u00f3 c\u00f3 bao g\u1ed3m c\u00e1c d\u1eef li\u1ec7u c\u00f3 quan h\u1ec7 li\u00ean quan m\u1eadt thi\u1ebft hay g\u1ecdi l\u00e0 b\u1ea3ng ghi.<\/li>\n<li aria-level=\"1\">C\u1ed9t\/ tr\u01b0\u1eddng: \u0110\u01b0\u1ee3c vi\u1ebft t\u1eaft l\u00e0 Field, h\u1ea7u h\u1ebft nh\u1eefng c\u1ed9t\/ tr\u01b0\u1eddng n\u00e0y \u0111\u1ec1u th\u1ec3 hi\u1ec7n thu\u1ed9c t\u00ednh c\u1ee7a b\u1ea3ng d\u1eef li\u1ec7u v\u00ed d\u1ee5 nh\u01b0: \u0111\u1ecba ch\u1ec9, t\u00ean tu\u1ed5i,\u2026<\/li>\n<li aria-level=\"1\">\u00d4: C\u00e1c \u00f4 \u0111\u01b0\u1ee3c giao nhau gi\u1eefa d\u00f2ng v\u00e0 c\u1ed9t \u0111\u1ec1u l\u00e0 n\u01a1i ch\u1ee9a d\u1eef li\u1ec7u.<\/li>\n<li aria-level=\"1\">Kh\u00f3a ch\u00ednh: C\u00e1c ph\u1ea7n kh\u00f3a ch\u00ednh hay c\u00f2n \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 primary key, \u0111\u00e2y l\u00e0 s\u1ef1 xu\u1ea5t hi\u1ec7n c\u1ee7a m\u1ed9t tr\u01b0\u1eddng ho\u1eb7c nhi\u1ec1u tr\u01b0\u1eddng k\u1ebft h\u1ee3p l\u1ea1i \u0111\u1ec3 \u0111\u1ecbnh ngh\u0129a b\u1ea3ng ghi. C\u00f2n \u0111\u1ed1i v\u1edbi kh\u00f3a ch\u00ednh s\u1ebd c\u00f3 2 thu\u1ed9c t\u00ednh ri\u00eang \u0111\u00f3 l\u00e0 kh\u00f4ng \u0111\u01b0\u1ee3c tr\u00f9ng l\u1eb7p v\u00e0 kh\u00f4ng \u0111\u01b0\u1ee3c \u0111\u1ec3 r\u1ed7ng.<\/li>\n<\/ul>\n<h3 id=\"ftoc-heading-6\" class=\"ftwp-heading\"><b>M\u1ed1i quan h\u1ec7\u00a0<\/b><\/h3>\n<p>Th\u00e0nh ph\u1ea7n m\u1ed1i quan h\u1ec7 trong c\u01a1 s\u1edf d\u1eef li\u1ec7u s\u1ebd bao g\u1ed3m nh\u1eefng y\u1ebfu t\u1ed1 ch\u00ednh nh\u01b0 sau:<\/p>\n<ul>\n<li aria-level=\"1\">Kh\u00f3a ngo\u1ea1i: C\u00f2n \u0111\u01b0\u1ee3c bi\u1ebft \u0111\u1ebfn v\u1edbi m\u1ed9t t\u00ean g\u1ecdi kh\u00e1c l\u00e0 Foreign Key l\u00e0 tr\u01b0\u1eddng \u1edf trong b\u1ea3ng n\u00e0y nh\u01b0ng n\u00f3 l\u1ea1i c\u00f3 tr\u01b0\u1eddng t\u01b0\u01a1ng \u1ee9ng l\u00e0m kh\u00f3a ch\u00ednh \u1edf c\u1ea3 ph\u1ea7n b\u1ea3ng kia. T\u1eeb \u0111\u00f3, \u0111\u1ec3 t\u1ea1o n\u00ean m\u1ed1i quan h\u1ec7 m\u1eadt thi\u1ebft gi\u1eefa hai b\u1ea3ng n\u00e0y v\u1edbi nhau.<\/li>\n<li aria-level=\"1\">M\u1ed1i quan h\u1ec7: M\u1ed1i quan h\u1ec7 n\u00e0y hay c\u00f2n g\u1ecdi l\u00e0 relationship \u0111\u01b0\u1ee3c t\u1ea1o ra m\u1ed1i li\u00ean k\u1ebft gi\u1eefa hai b\u1ea3ng \u0111\u1ec3 nh\u1eb1m h\u01b0\u1edbng \u0111\u1ebfn m\u1ed1i li\u00ean quan gi\u1eefa c\u00e1c tr\u01b0\u1eddng d\u1eef li\u1ec7u \u1edf hai b\u1ea3ng.<\/li>\n<\/ul>\n<h2 id=\"ftoc-heading-7\" class=\"ftwp-heading\"><b>Nh\u1eefng l\u1ee3i \u00edch c\u1ee7a c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 l\u00e0 g\u00ec?<\/b><\/h2>\n<p>T\u1ea1i sao <a href=\"https:\/\/vi.wikipedia.org\/wiki\/C%C6%A1_s%E1%BB%9F_d%E1%BB%AF_li%E1%BB%87u\" target=\"_blank\" rel=\"nofollow noopener\">c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/a> quan h\u1ec7 l\u1ea1i \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng ph\u1ed5 bi\u1ebfn v\u00e0 r\u1ed9ng r\u00e3i nh\u01b0 th\u1ebf. B\u1edfi ch\u00fang \u0111em \u0111\u1ebfn nh\u1eefng l\u1ee3i \u00edch \u0111\u1eb7c bi\u1ec7t v\u00e0 quan tr\u1ecdng m\u00e0 nh\u1eefng d\u1eef li\u1ec7u kh\u00e1c kh\u00f4ng th\u1ec3 n\u00e0o l\u00e0m \u0111\u01b0\u1ee3c. Trong \u0111\u00f3, ch\u00fang ta c\u00f3 th\u1ec3 k\u1ec3 \u0111\u1ebfn m\u1ed9t v\u00e0i l\u1ee3i \u00edch ch\u1eb3ng h\u1ea1n:<\/p>\n<ul>\n<li aria-level=\"1\">Gi\u00fap cho t\u1ea5t c\u1ea3 c\u00e1c d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef c\u00f3 t\u1ed5 ch\u1ee9c v\u00e0 hi\u1ec7u qu\u1ea3 h\u01a1n.<\/li>\n<li aria-level=\"1\">\u0110\u1ea3m b\u1ea3o \u0111\u01b0\u1ee3c t\u00ednh th\u1ed1ng nh\u1ea5t trong c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7.<\/li>\n<li aria-level=\"1\">C\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 s\u1ebd h\u1ea1n ch\u1ebf \u0111\u01b0\u1ee3c s\u1ef1 tr\u00f9ng l\u1eb7p d\u1eef li\u1ec7u ho\u1eb7c d\u01b0 th\u1eeba d\u1eef li\u1ec7u \u0111i.<\/li>\n<li aria-level=\"1\">T\u1ea5t c\u1ea3 c\u00e1c d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c l\u01b0u tr\u1eef \u0111\u1ec1u c\u00f3 th\u1ec3 chia s\u1ebb v\u1edbi nhau \u0111\u01b0\u1ee3c.<\/li>\n<li aria-level=\"1\">\u0110\u1ea3m b\u1ea3o \u0111\u01b0\u1ee3c t\u00ednh b\u1ea3o m\u1eadt c\u1ee7a d\u1eef li\u1ec7u.<\/li>\n<li aria-level=\"1\">Gi\u00fap duy tr\u00ec \u0111\u01b0\u1ee3c t\u00ednh to\u00e0n v\u1eb9n c\u1ee7a c\u00e1c d\u1eef li\u1ec7u n\u00e0y.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>C\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 l\u00e0 g\u00ec? M\u1ee5c \u0111\u00edch c\u1ee7a c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 l\u00e0 \u0111em \u0111\u1ebfn t\u00ednh hi\u1ec7u qu\u1ea3 cho t\u1ed5 ch\u1ee9c v\u00e0 t\u00ednh ch\u00ednh x\u00e1c c\u1ee7a n\u00f3. Kh\u00e1i ni\u1ec7m c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7\u00a0 Ch\u00fang ta c\u00f3 th\u1ec3 n\u1eafm b\u1eaft \u0111\u01b0\u1ee3c kh\u00e1i ni\u1ec7m\u00a0c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 l\u00e0 [&hellip;]<\/p>\n","protected":false},"author":3,"featured_media":5468,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[4],"tags":[461,462],"class_list":["post-5436","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-content","tag-co-so-du-lieu","tag-co-so-du-lieu-quan-he"],"jetpack_featured_media_url":"https:\/\/webvocuc.com\/blog\/wp-content\/uploads\/2021\/12\/he-quan-tri-co-so-du-lieu-la-gi.jpg","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/webvocuc.com\/blog\/wp-json\/wp\/v2\/posts\/5436","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/webvocuc.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/webvocuc.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/webvocuc.com\/blog\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/webvocuc.com\/blog\/wp-json\/wp\/v2\/comments?post=5436"}],"version-history":[{"count":9,"href":"https:\/\/webvocuc.com\/blog\/wp-json\/wp\/v2\/posts\/5436\/revisions"}],"predecessor-version":[{"id":5517,"href":"https:\/\/webvocuc.com\/blog\/wp-json\/wp\/v2\/posts\/5436\/revisions\/5517"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/webvocuc.com\/blog\/wp-json\/wp\/v2\/media\/5468"}],"wp:attachment":[{"href":"https:\/\/webvocuc.com\/blog\/wp-json\/wp\/v2\/media?parent=5436"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/webvocuc.com\/blog\/wp-json\/wp\/v2\/categories?post=5436"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/webvocuc.com\/blog\/wp-json\/wp\/v2\/tags?post=5436"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}