{"id":923209,"date":"2024-07-01T07:00:51","date_gmt":"2024-07-01T07:00:51","guid":{"rendered":"https:\/\/proxyelite.info\/?p=923209"},"modified":"2024-06-25T07:03:20","modified_gmt":"2024-06-25T07:03:20","slug":"understanding-indexes-in-databases","status":"publish","type":"post","link":"https:\/\/proxyelite.info\/vi\/understanding-indexes-in-databases\/","title":{"rendered":"Hi\u1ec3u ch\u1ec9 m\u1ee5c trong c\u01a1 s\u1edf d\u1eef li\u1ec7u"},"content":{"rendered":"<p class=\"wp-block-paragraph\">Ch\u1ec9 m\u1ee5c l\u00e0 th\u00e0nh ph\u1ea7n c\u01a1 b\u1ea3n c\u1ee7a c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf \u0111\u1ec3 n\u00e2ng cao t\u1ed1c \u0111\u1ed9 ho\u1ea1t \u0111\u1ed9ng truy xu\u1ea5t d\u1eef li\u1ec7u. Ch\u00fang \u0111\u00f3ng vai tr\u00f2 l\u00e0 c\u1ea5u tr\u00fac d\u1eef li\u1ec7u gi\u00fap c\u1ea3i thi\u1ec7n hi\u1ec7u qu\u1ea3 c\u1ee7a c\u00e1c truy v\u1ea5n c\u01a1 s\u1edf d\u1eef li\u1ec7u b\u1eb1ng c\u00e1ch cung c\u1ea5p quy\u1ec1n truy c\u1eadp nhanh v\u00e0o c\u00e1c h\u00e0ng trong b\u1ea3ng.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">C\u00e1ch th\u1ee9c ho\u1ea1t \u0111\u1ed9ng c\u1ee7a ch\u1ec9 m\u1ee5c<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Ch\u1ec9 m\u1ee5c ho\u1ea1t \u0111\u1ed9ng t\u01b0\u01a1ng t\u1ef1 nh\u01b0 ch\u1ec9 m\u1ee5c trong m\u1ed9t cu\u1ed1n s\u00e1ch. Thay v\u00ec qu\u00e9t to\u00e0n b\u1ed9 b\u1ea3ng \u0111\u1ec3 t\u00ecm d\u1eef li\u1ec7u c\u1ea7n thi\u1ebft, c\u01a1 s\u1edf d\u1eef li\u1ec7u s\u1eed d\u1ee5ng ch\u1ec9 m\u1ee5c \u0111\u1ec3 nhanh ch\u00f3ng x\u00e1c \u0111\u1ecbnh v\u1ecb tr\u00ed c\u00e1c h\u00e0ng mong mu\u1ed1n. C\u00e1c ch\u1ec9 m\u1ee5c th\u01b0\u1eddng \u0111\u01b0\u1ee3c t\u1ea1o tr\u00ean c\u00e1c c\u1ed9t th\u01b0\u1eddng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong m\u1ec7nh \u0111\u1ec1 WHERE, \u0111i\u1ec1u ki\u1ec7n THAM GIA v\u00e0 m\u1ec7nh \u0111\u1ec1 ORDER BY.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">C\u1ea5u tr\u00fac ch\u1ec9 m\u1ee5c<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">C\u00e1c ch\u1ec9 m\u1ee5c th\u01b0\u1eddng \u0111\u01b0\u1ee3c tri\u1ec3n khai d\u01b0\u1edbi d\u1ea1ng c\u00e2y B ho\u1eb7c b\u1ea3ng b\u0103m:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>c\u00e2y B<\/strong>: C\u1ea5u tr\u00fac c\u00e2y c\u00e2n b\u1eb1ng duy tr\u00ec th\u1ee9 t\u1ef1 \u0111\u01b0\u1ee3c s\u1eafp x\u1ebfp v\u00e0 cho ph\u00e9p \u0111\u1ed9 ph\u1ee9c t\u1ea1p v\u1ec1 th\u1eddi gian logarit cho c\u00e1c ho\u1ea1t \u0111\u1ed9ng t\u00ecm ki\u1ebfm, ch\u00e8n v\u00e0 x\u00f3a.<\/li>\n\n\n\n<li><strong>B\u1ea3ng b\u0103m<\/strong>: Cung c\u1ea5p \u0111\u1ed9 ph\u1ee9c t\u1ea1p v\u1ec1 th\u1eddi gian kh\u00f4ng \u0111\u1ed5i cho c\u00e1c ho\u1ea1t \u0111\u1ed9ng t\u00ecm ki\u1ebfm nh\u01b0ng k\u00e9m linh ho\u1ea1t h\u01a1n c\u00e2y B cho c\u00e1c truy v\u1ea5n ph\u1ea1m vi.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">C\u00e1c lo\u1ea1i ch\u1ec9 m\u1ee5c<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">C\u00f3 m\u1ed9t s\u1ed1 lo\u1ea1i ch\u1ec9 m\u1ee5c, m\u1ed7i lo\u1ea1i ph\u1ee5c v\u1ee5 c\u00e1c m\u1ee5c \u0111\u00edch kh\u00e1c nhau:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Ch\u1ec9 s\u1ed1 ch\u00ednh<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Ch\u1ec9 s\u1ed1 ch\u00ednh<\/strong>: \u0110\u01b0\u1ee3c t\u1ea1o t\u1ef1 \u0111\u1ed9ng khi kh\u00f3a ch\u00ednh \u0111\u01b0\u1ee3c x\u00e1c \u0111\u1ecbnh. N\u00f3 x\u00e1c \u0111\u1ecbnh duy nh\u1ea5t m\u1ed7i h\u00e0ng trong m\u1ed9t b\u1ea3ng.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Ch\u1ec9 s\u1ed1 ph\u1ee5<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Ch\u1ec9 s\u1ed1 ph\u1ee5<\/strong>: \u0110\u01b0\u1ee3c t\u1ea1o tr\u00ean c\u00e1c c\u1ed9t kh\u00f3a kh\u00f4ng ch\u00ednh \u0111\u1ec3 c\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t c\u1ee7a c\u00e1c truy v\u1ea5n li\u00ean quan \u0111\u1ebfn c\u00e1c c\u1ed9t \u0111\u00f3.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Ch\u1ec9 m\u1ee5c duy nh\u1ea5t<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Ch\u1ec9 m\u1ee5c duy nh\u1ea5t<\/strong>: \u0110\u1ea3m b\u1ea3o r\u1eb1ng (c\u00e1c) c\u1ed9t \u0111\u01b0\u1ee3c l\u1eadp ch\u1ec9 m\u1ee5c ch\u1ee9a c\u00e1c gi\u00e1 tr\u1ecb duy nh\u1ea5t, ng\u0103n ch\u1eb7n c\u00e1c m\u1ee5c nh\u1eadp tr\u00f9ng l\u1eb7p.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Ch\u1ec9 s\u1ed1 t\u1ed5ng h\u1ee3p<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Ch\u1ec9 s\u1ed1 t\u1ed5ng h\u1ee3p<\/strong>: Ch\u1ec9 m\u1ee5c tr\u00ean nhi\u1ec1u c\u1ed9t, h\u1eefu \u00edch cho c\u00e1c truy v\u1ea5n l\u1ecdc ho\u1eb7c s\u1eafp x\u1ebfp d\u1ef1a tr\u00ean nhi\u1ec1u c\u1ed9t.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Ch\u1ec9 m\u1ee5c to\u00e0n v\u0103n<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Ch\u1ec9 m\u1ee5c to\u00e0n v\u0103n<\/strong>: \u0110\u01b0\u1ee3c thi\u1ebft k\u1ebf \u0111\u1ec3 t\u00ecm ki\u1ebfm v\u0103n b\u1ea3n hi\u1ec7u qu\u1ea3 trong c\u00e1c tr\u01b0\u1eddng v\u0103n b\u1ea3n l\u1edbn.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Ch\u1ec9 m\u1ee5c bitmap<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Ch\u1ec9 m\u1ee5c bitmap<\/strong>: Hi\u1ec7u qu\u1ea3 cho c\u00e1c c\u1ed9t c\u00f3 s\u1ed1 l\u01b0\u1ee3ng gi\u00e1 tr\u1ecb ri\u00eang bi\u1ec7t h\u1ea1n ch\u1ebf, th\u01b0\u1eddng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong kho d\u1eef li\u1ec7u.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">T\u00e1c \u0111\u1ed9ng c\u1ee7a ch\u1ec9 m\u1ee5c \u0111\u1ed1i v\u1edbi truy v\u1ea5n CH\u1eccN<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">C\u00e1c ch\u1ec9 m\u1ee5c c\u00f3 th\u1ec3 c\u1ea3i thi\u1ec7n \u0111\u00e1ng k\u1ec3 hi\u1ec7u su\u1ea5t c\u1ee7a c\u00e1c truy v\u1ea5n CH\u1eccN b\u1eb1ng c\u00e1ch gi\u1ea3m l\u01b0\u1ee3ng d\u1eef li\u1ec7u \u0111\u01b0\u1ee3c qu\u00e9t:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Truy xu\u1ea5t d\u1eef li\u1ec7u nhanh h\u01a1n<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Ch\u1ec9 m\u1ee5c cho ph\u00e9p c\u01a1 s\u1edf d\u1eef li\u1ec7u nhanh ch\u00f3ng x\u00e1c \u0111\u1ecbnh v\u1ecb tr\u00ed c\u00e1c h\u00e0ng ph\u00f9 h\u1ee3p v\u1edbi ti\u00eau ch\u00ed truy v\u1ea5n m\u00e0 kh\u00f4ng c\u1ea7n ph\u1ea3i qu\u00e9t to\u00e0n b\u1ed9 b\u1ea3ng. \u0110i\u1ec1u n\u00e0y \u0111\u1eb7c bi\u1ec7t c\u00f3 l\u1ee3i cho c\u00e1c b\u00e0n l\u1edbn.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">V\u00ed d\u1ee5<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">H\u00e3y xem x\u00e9t m\u1ed9t b\u1ea3ng <code data-no-translation=\"\">employees<\/code> v\u1edbi c\u00e1c c\u1ed9t <code data-no-translation=\"\">id<\/code>, <code data-no-translation=\"\">name<\/code>, V\u00e0 <code data-no-translation=\"\">department<\/code>. M\u1ed9t truy v\u1ea5n \u0111\u1ec3 t\u00ecm nh\u00e2n vi\u00ean trong m\u1ed9t b\u1ed9 ph\u1eadn c\u1ee5 th\u1ec3:<\/p>\n\n\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-sql\" data-lang=\"SQL\"><code data-no-translation=\"\">SELECT * FROM employees WHERE department = &#39;Sales&#39;;\n<\/code><\/pre><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">Kh\u00f4ng c\u00f3 ch\u1ec9 m\u1ee5c tr\u00ean <code data-no-translation=\"\">department<\/code> c\u1ed9t, c\u01a1 s\u1edf d\u1eef li\u1ec7u s\u1ebd qu\u00e9t to\u00e0n b\u1ed9 b\u1ea3ng. V\u1edbi m\u1ed9t ch\u1ec9 m\u1ee5c, n\u00f3 nhanh ch\u00f3ng t\u00ecm th\u1ea5y c\u00e1c h\u00e0ng c\u00f3 li\u00ean quan.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Gi\u1ea3m ho\u1ea1t \u0111\u1ed9ng I\/O<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">C\u00e1c ch\u1ec9 m\u1ee5c l\u00e0m gi\u1ea3m s\u1ed1 l\u01b0\u1ee3ng thao t\u00e1c I\/O c\u1ea7n thi\u1ebft \u0111\u1ec3 t\u00ecm n\u1ea1p d\u1eef li\u1ec7u t\u1eeb \u0111\u0129a, d\u1eabn \u0111\u1ebfn vi\u1ec7c th\u1ef1c thi truy v\u1ea5n nhanh h\u01a1n.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">T\u00e1c \u0111\u1ed9ng c\u1ee7a ch\u1ec9 m\u1ee5c \u0111\u1ed1i v\u1edbi c\u00e1c ho\u1ea1t \u0111\u1ed9ng CH\u00c8N, C\u1eacP NH\u1eacT, X\u00d3A<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">M\u1eb7c d\u00f9 c\u00e1c ch\u1ec9 m\u1ee5c c\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t truy v\u1ea5n SELECT nh\u01b0ng ch\u00fang c\u00f3 th\u1ec3 c\u00f3 t\u00e1c \u0111\u1ed9ng ti\u00eau c\u1ef1c \u0111\u1ebfn hi\u1ec7u su\u1ea5t c\u1ee7a c\u00e1c ho\u1ea1t \u0111\u1ed9ng s\u1eeda \u0111\u1ed5i d\u1eef li\u1ec7u:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Ho\u1ea1t \u0111\u1ed9ng INSERT ch\u1eadm h\u01a1n<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Khi ch\u00e8n h\u00e0ng m\u1edbi, c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u1ea3i c\u1eadp nh\u1eadt ch\u1ec9 m\u1ee5c \u0111\u1ec3 bao g\u1ed3m c\u00e1c m\u1ee5c m\u1edbi. B\u01b0\u1edbc b\u1ed5 sung n\u00e0y c\u00f3 th\u1ec3 l\u00e0m ch\u1eadm qu\u00e1 tr\u00ecnh ch\u00e8n.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">V\u00ed d\u1ee5<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u0110\u01b0a m\u1ed9t nh\u00e2n vi\u00ean m\u1edbi v\u00e0o <code data-no-translation=\"\">employees<\/code> b\u00e0n:<\/p>\n\n\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-sql\" data-lang=\"SQL\"><code data-no-translation=\"\">INSERT INTO employees (id, name, department) VALUES (101, &#39;John Doe&#39;, &#39;Sales&#39;);\n<\/code><\/pre><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">N\u1ebfu c\u00f3 m\u1ed9t ch\u1ec9 m\u1ee5c tr\u00ean <code data-no-translation=\"\">department<\/code> c\u1ed9t, c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u1ea3i c\u1eadp nh\u1eadt ch\u1ec9 m\u1ee5c, b\u1ed5 sung chi ph\u00ed cho qu\u00e1 tr\u00ecnh ch\u00e8n.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Ho\u1ea1t \u0111\u1ed9ng C\u1eacP NH\u1eacT ch\u1eadm h\u01a1n<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">C\u1eadp nh\u1eadt c\u00e1c c\u1ed9t \u0111\u01b0\u1ee3c l\u1eadp ch\u1ec9 m\u1ee5c y\u00eau c\u1ea7u c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1eadp nh\u1eadt c\u00e1c m\u1ee5c ch\u1ec9 m\u1ee5c t\u01b0\u01a1ng \u1ee9ng. \u0110i\u1ec1u n\u00e0y c\u00f3 th\u1ec3 l\u00e0m ch\u1eadm qu\u00e1 tr\u00ecnh c\u1eadp nh\u1eadt, \u0111\u1eb7c bi\u1ec7t \u0111\u1ed1i v\u1edbi c\u00e1c b\u1ea3ng l\u1edbn c\u00f3 nhi\u1ec1u ch\u1ec9 m\u1ee5c.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Thao t\u00e1c DELETE ch\u1eadm h\u01a1n<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">T\u01b0\u01a1ng t\u1ef1 nh\u01b0 c\u00e1c b\u1ea3n c\u1eadp nh\u1eadt, vi\u1ec7c x\u00f3a c\u00e1c h\u00e0ng y\u00eau c\u1ea7u c\u01a1 s\u1edf d\u1eef li\u1ec7u x\u00f3a c\u00e1c m\u1ee5c nh\u1eadp t\u01b0\u01a1ng \u1ee9ng kh\u1ecfi ch\u1ec9 m\u1ee5c, th\u00eam chi ph\u00ed v\u00e0o qu\u00e1 tr\u00ecnh x\u00f3a.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">S\u1ef1 \u0111\u00e1nh \u0111\u1ed5i c\u1ee7a vi\u1ec7c s\u1eed d\u1ee5ng ch\u1ec9 m\u1ee5c<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Kh\u00f4ng gian tr\u00ean cao<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">C\u00e1c ch\u1ec9 m\u1ee5c y\u00eau c\u1ea7u kh\u00f4ng gian l\u01b0u tr\u1eef b\u1ed5 sung. B\u1ea3ng c\u00e0ng c\u00f3 nhi\u1ec1u ch\u1ec9 m\u1ee5c th\u00ec c\u00e0ng c\u1ea7n nhi\u1ec1u dung l\u01b0\u1ee3ng \u0111\u0129a \u0111\u1ec3 l\u01b0u tr\u1eef ch\u00fang.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Chi ph\u00ed b\u1ea3o tr\u00ec<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Vi\u1ec7c duy tr\u00ec c\u00e1c ch\u1ec9 m\u1ee5c trong qu\u00e1 tr\u00ecnh s\u1eeda \u0111\u1ed5i d\u1eef li\u1ec7u (CH\u00c8N, C\u1eacP NH\u1eacT, X\u00d3A) s\u1ebd l\u00e0m t\u0103ng th\u00eam chi ph\u00ed, c\u00f3 kh\u1ea3 n\u0103ng l\u00e0m ch\u1eadm c\u00e1c ho\u1ea1t \u0111\u1ed9ng n\u00e0y.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Ph\u00e2n m\u1ea3nh ch\u1ec9 m\u1ee5c<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Theo th\u1eddi gian, c\u00e1c ch\u1ec9 m\u1ee5c c\u00f3 th\u1ec3 b\u1ecb ph\u00e2n m\u1ea3nh, d\u1eabn \u0111\u1ebfn hi\u1ec7u su\u1ea5t gi\u1ea3m. C\u1ea7n ph\u1ea3i b\u1ea3o tr\u00ec th\u01b0\u1eddng xuy\u00ean, ch\u1eb3ng h\u1ea1n nh\u01b0 x\u00e2y d\u1ef1ng l\u1ea1i ho\u1eb7c s\u1eafp x\u1ebfp l\u1ea1i c\u00e1c ch\u1ec9 m\u1ee5c \u0111\u1ec3 duy tr\u00ec hi\u1ec7u su\u1ea5t t\u1ed1i \u01b0u.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Th\u1ef1c ti\u1ec5n t\u1ed1t nh\u1ea5t \u0111\u1ec3 s\u1eed d\u1ee5ng ch\u1ec9 m\u1ee5c<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">L\u1eadp ch\u1ec9 m\u1ee5c ch\u1ecdn l\u1ecdc<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Ch\u1ec9 t\u1ea1o ch\u1ec9 m\u1ee5c tr\u00ean c\u00e1c c\u1ed9t th\u01b0\u1eddng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong truy v\u1ea5n. Tr\u00e1nh l\u1eadp ch\u1ec9 m\u1ee5c c\u00e1c c\u1ed9t c\u00f3 \u0111\u1ed9 ch\u1ecdn l\u1ecdc th\u1ea5p (c\u1ed9t c\u00f3 nhi\u1ec1u gi\u00e1 tr\u1ecb tr\u00f9ng l\u1eb7p).<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Gi\u00e1m s\u00e1t v\u00e0 b\u1ea3o tr\u00ec<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Th\u01b0\u1eddng xuy\u00ean theo d\u00f5i hi\u1ec7u su\u1ea5t c\u1ee7a c\u00e1c ch\u1ec9 m\u1ee5c v\u00e0 th\u1ef1c hi\u1ec7n c\u00e1c t\u00e1c v\u1ee5 b\u1ea3o tr\u00ec, ch\u1eb3ng h\u1ea1n nh\u01b0 x\u00e2y d\u1ef1ng l\u1ea1i c\u00e1c ch\u1ec9 m\u1ee5c b\u1ecb ph\u00e2n m\u1ea3nh, \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o hi\u1ec7u su\u1ea5t t\u1ed1i \u01b0u.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Ch\u1ec9 s\u1ed1 t\u1ed5ng h\u1ee3p<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">H\u00e3y c\u00e2n nh\u1eafc s\u1eed d\u1ee5ng ch\u1ec9 m\u1ee5c t\u1ed5ng h\u1ee3p cho c\u00e1c truy v\u1ea5n l\u1ecdc ho\u1eb7c s\u1eafp x\u1ebfp d\u1ef1a tr\u00ean nhi\u1ec1u c\u1ed9t. Tuy nhi\u00ean, h\u00e3y ch\u00fa \u00fd \u0111\u1ebfn th\u1ee9 t\u1ef1 c\u00e1c c\u1ed9t trong ch\u1ec9 m\u1ee5c t\u1ed5ng h\u1ee3p v\u00ec n\u00f3 \u1ea3nh h\u01b0\u1edfng \u0111\u1ebfn hi\u1ec7u qu\u1ea3 c\u1ee7a ch\u1ec9 m\u1ee5c.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Tr\u00e1nh l\u1eadp ch\u1ec9 m\u1ee5c qu\u00e1 m\u1ee9c<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Trong khi c\u00e1c ch\u1ec9 m\u1ee5c c\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t truy v\u1ea5n, vi\u1ec7c l\u1eadp ch\u1ec9 m\u1ee5c qu\u00e1 m\u1ee9c c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn chi ph\u00ed b\u1ea3o tr\u00ec \u0111\u00e1ng k\u1ec3. Ph\u1ea5n \u0111\u1ea5u c\u00e2n b\u1eb1ng gi\u1eefa hi\u1ec7u su\u1ea5t truy v\u1ea5n v\u00e0 chi ph\u00ed b\u1ea3o tr\u00ec.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Ph\u1ea7n k\u1ebft lu\u1eadn<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Ch\u1ec9 m\u1ee5c l\u00e0 c\u00f4ng c\u1ee5 m\u1ea1nh m\u1ebd \u0111\u1ec3 t\u1ed1i \u01b0u h\u00f3a hi\u1ec7u su\u1ea5t c\u01a1 s\u1edf d\u1eef li\u1ec7u, \u0111\u1eb7c bi\u1ec7t \u0111\u1ed1i v\u1edbi c\u00e1c truy v\u1ea5n SELECT. Ch\u00fang cung c\u1ea5p quy\u1ec1n truy c\u1eadp nhanh v\u00e0o d\u1eef li\u1ec7u v\u00e0 gi\u1ea3m nhu c\u1ea7u qu\u00e9t to\u00e0n b\u1ed9 b\u1ea3ng. Tuy nhi\u00ean, ch\u00fang c\u0169ng g\u00e2y ra chi ph\u00ed cho c\u00e1c ho\u1ea1t \u0111\u1ed9ng s\u1eeda \u0111\u1ed5i d\u1eef li\u1ec7u v\u00e0 y\u00eau c\u1ea7u qu\u1ea3n l\u00fd c\u1ea9n th\u1eadn \u0111\u1ec3 tr\u00e1nh suy gi\u1ea3m hi\u1ec7u su\u1ea5t. B\u1eb1ng c\u00e1ch hi\u1ec3u \u0111\u01b0\u1ee3c s\u1ef1 c\u00e2n b\u1eb1ng v\u00e0 tu\u00e2n theo c\u00e1c ph\u01b0\u01a1ng ph\u00e1p hay nh\u1ea5t, c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n c\u00f3 th\u1ec3 t\u1eadn d\u1ee5ng c\u00e1c ch\u1ec9 m\u1ee5c m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3 \u0111\u1ec3 n\u00e2ng cao hi\u1ec7u qu\u1ea3 c\u1ee7a c\u00e1c \u1ee9ng d\u1ee5ng c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a h\u1ecd.<\/p>","protected":false},"excerpt":{"rendered":"<p>Indexes are fundamental components of relational databases designed to enhance the speed of data retrieval operations. They serve as data structures that improve the efficiency of database queries by providing quick access to rows in a table. How Indexes Work An index works similarly to an index in a book. Instead of scanning the entire [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":923210,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-923209","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-articles"],"acf":[],"_links":{"self":[{"href":"https:\/\/proxyelite.info\/vi\/wp-json\/wp\/v2\/posts\/923209","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/proxyelite.info\/vi\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/proxyelite.info\/vi\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/proxyelite.info\/vi\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/proxyelite.info\/vi\/wp-json\/wp\/v2\/comments?post=923209"}],"version-history":[{"count":0,"href":"https:\/\/proxyelite.info\/vi\/wp-json\/wp\/v2\/posts\/923209\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/proxyelite.info\/vi\/wp-json\/wp\/v2\/media\/923210"}],"wp:attachment":[{"href":"https:\/\/proxyelite.info\/vi\/wp-json\/wp\/v2\/media?parent=923209"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/proxyelite.info\/vi\/wp-json\/wp\/v2\/categories?post=923209"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/proxyelite.info\/vi\/wp-json\/wp\/v2\/tags?post=923209"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}