{"id":476734,"date":"2023-08-09T07:35:16","date_gmt":"2023-08-09T07:35:16","guid":{"rendered":""},"modified":"2023-09-05T11:13:20","modified_gmt":"2023-09-05T11:13:20","slug":"database-index","status":"publish","type":"wiki","link":"https:\/\/oneproxy.pro\/vn\/wiki\/database-index\/","title":{"rendered":"Ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u"},"content":{"rendered":"<p>L\u1eadp ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u l\u00e0 m\u1ed9t kh\u00eda c\u1ea1nh quan tr\u1ecdng c\u1ee7a h\u1ec7 th\u1ed1ng qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u (DBMS) gi\u00fap n\u00e2ng cao t\u1ed1c \u0111\u1ed9 v\u00e0 hi\u1ec7u su\u1ea5t c\u1ee7a c\u00e1c ho\u1ea1t \u0111\u1ed9ng truy xu\u1ea5t d\u1eef li\u1ec7u. Ch\u1ec9 m\u1ee5c cung c\u1ea5p \u0111\u01b0\u1eddng d\u1eabn tra c\u1ee9u nhanh ch\u00f3ng t\u1edbi d\u1eef li\u1ec7u, gi\u1ea3m l\u01b0\u1ee3ng th\u1eddi gian c\u1ea7n thi\u1ebft \u0111\u1ec3 t\u00ecm b\u1ea3n ghi.<\/p>\n<h2>B\u1ed1i c\u1ea3nh l\u1ecbch s\u1eed c\u1ee7a ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/h2>\n<p>Kh\u00e1i ni\u1ec7m l\u1eadp ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u xu\u1ea5t hi\u1ec7n c\u00f9ng v\u1edbi s\u1ef1 ph\u00e1t tri\u1ec3n c\u1ee7a h\u1ec7 th\u1ed1ng qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u. Ngay t\u1eeb nh\u1eefng n\u0103m 1960, v\u1edbi s\u1ef1 ra \u0111\u1eddi c\u1ee7a h\u1ec7 th\u1ed1ng l\u01b0u tr\u1eef d\u1ef1a tr\u00ean \u0111\u0129a, nhu c\u1ea7u v\u1ec1 c\u00e1c ph\u01b0\u01a1ng ph\u00e1p truy xu\u1ea5t d\u1eef li\u1ec7u hi\u1ec7u qu\u1ea3 \u0111\u00e3 tr\u1edf n\u00ean r\u00f5 r\u00e0ng. L\u1ea7n \u0111\u1ea7u ti\u00ean \u0111\u1ec1 c\u1eadp \u0111\u1ebfn kh\u00e1i ni\u1ec7m &#039;ch\u1ec9 m\u1ee5c&#039; trong b\u1ed1i c\u1ea3nh truy xu\u1ea5t d\u1eef li\u1ec7u c\u00f3 th\u1ec3 b\u1eaft ngu\u1ed3n t\u1eeb c\u00e1c m\u00f4 h\u00ecnh c\u01a1 s\u1edf d\u1eef li\u1ec7u s\u1edbm nh\u1ea5t, bao g\u1ed3m c\u01a1 s\u1edf d\u1eef li\u1ec7u m\u1ea1ng v\u00e0 ph\u00e2n c\u1ea5p.<\/p>\n<p>Tuy nhi\u00ean, ch\u00ednh trong b\u1ed1i c\u1ea3nh c\u1ee7a m\u00f4 h\u00ecnh c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 do Edgar F. Codd \u0111\u1ec1 xu\u1ea5t v\u00e0o n\u0103m 1970, c\u00e1c ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u \u0111\u00e3 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng r\u1ed9ng r\u00e3i. System R c\u1ee7a IBM, m\u1ed9t h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 th\u1eed nghi\u1ec7m, l\u00e0 m\u1ed9t trong nh\u1eefng h\u1ec7 th\u1ed1ng \u0111\u1ea7u ti\u00ean tri\u1ec3n khai vi\u1ec7c s\u1eed d\u1ee5ng c\u00e1c ch\u1ec9 m\u1ee5c \u0111\u1ec3 t\u0103ng t\u1ed1c \u0111\u1ed9 truy xu\u1ea5t d\u1eef li\u1ec7u.<\/p>\n<h2>\u0110i s\u00e2u h\u01a1n v\u00e0o ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/h2>\n<p>Ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u l\u00e0 m\u1ed9t c\u1ea5u tr\u00fac d\u1eef li\u1ec7u gi\u00fap n\u00e2ng cao t\u1ed1c \u0111\u1ed9 c\u1ee7a c\u00e1c ho\u1ea1t \u0111\u1ed9ng truy xu\u1ea5t d\u1eef li\u1ec7u tr\u00ean b\u1ea3ng c\u01a1 s\u1edf d\u1eef li\u1ec7u. T\u01b0\u01a1ng t\u1ef1 nh\u01b0 ch\u1ec9 m\u1ee5c trong m\u1ed9t cu\u1ed1n s\u00e1ch cho ph\u00e9p b\u1ea1n nhanh ch\u00f3ng t\u00ecm th\u1ea5y m\u1ed9t ch\u1ee7 \u0111\u1ec1 m\u00e0 kh\u00f4ng c\u1ea7n ph\u1ea3i \u0111\u1ecdc qua t\u1eebng trang, ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u cho ph\u00e9p DBMS t\u00ecm v\u00e0 truy xu\u1ea5t d\u1eef li\u1ec7u m\u00e0 kh\u00f4ng c\u1ea7n qu\u00e9t t\u1eebng h\u00e0ng trong b\u1ea3ng c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n<p>Ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u ho\u1ea1t \u0111\u1ed9ng b\u1eb1ng c\u00e1ch l\u01b0u tr\u1eef m\u1ed9t t\u1eadp h\u1ee3p con d\u1eef li\u1ec7u c\u1ee7a c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 duy tr\u00ec m\u1ed9t con tr\u1ecf t\u1edbi v\u1ecb tr\u00ed c\u1ee7a t\u1eebng ph\u1ea7n d\u1eef li\u1ec7u. Ch\u1ec9 m\u1ee5c l\u01b0u tr\u1eef d\u1eef li\u1ec7u c\u1ee7a n\u00f3 d\u1ef1a tr\u00ean c\u00e1c gi\u00e1 tr\u1ecb c\u1ee7a c\u00e1c c\u1ed9t \u0111\u01b0\u1ee3c l\u1eadp ch\u1ec9 m\u1ee5c, s\u1eafp x\u1ebfp ch\u00fang \u0111\u1ec3 cho ph\u00e9p truy xu\u1ea5t hi\u1ec7u qu\u1ea3. K\u1ebft qu\u1ea3 l\u00e0, khi m\u1ed9t truy v\u1ea5n \u0111\u01b0\u1ee3c th\u1ef1c thi, c\u00f4ng c\u1ee5 c\u01a1 s\u1edf d\u1eef li\u1ec7u tr\u01b0\u1edbc ti\u00ean s\u1ebd qu\u00e9t ch\u1ec9 m\u1ee5c \u0111\u1ec3 t\u00ecm v\u1ecb tr\u00ed c\u1ee7a d\u1eef li\u1ec7u thay v\u00ec qu\u00e9t to\u00e0n b\u1ed9 b\u1ea3ng c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n<p>\u0110i\u1ec1u n\u00e0y l\u00e0m gi\u1ea3m \u0111\u00e1ng k\u1ec3 s\u1ed1 l\u01b0\u1ee3ng ho\u1ea1t \u0111\u1ed9ng I\/O c\u1ee7a \u0111\u0129a, t\u0103ng t\u1ed1c \u0111\u1ed9 truy xu\u1ea5t d\u1eef li\u1ec7u. Tuy nhi\u00ean, \u0111i\u1ec1u \u0111\u00e1ng ch\u00fa \u00fd l\u00e0 c\u00e1c ch\u1ec9 s\u1ed1 c\u0169ng c\u00f3 s\u1ef1 \u0111\u00e1nh \u0111\u1ed5i c\u1ee7a ch\u00fang. Trong khi ch\u00fang t\u0103ng t\u1ed1c c\u00e1c thao t\u00e1c \u0111\u1ecdc, ch\u00fang c\u00f3 th\u1ec3 l\u00e0m ch\u1eadm c\u00e1c thao t\u00e1c ghi (ch\u00e8n, c\u1eadp nh\u1eadt, x\u00f3a) v\u00ec m\u1ed7i thao t\u00e1c ghi b\u00e2y gi\u1edd c\u0169ng c\u1ea7n c\u1eadp nh\u1eadt ch\u1ec9 m\u1ee5c.<\/p>\n<h2>C\u1ea5u tr\u00fac b\u00ean trong c\u1ee7a ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 c\u01a1 ch\u1ebf ho\u1ea1t \u0111\u1ed9ng c\u1ee7a n\u00f3<\/h2>\n<p>C\u1ea5u tr\u00fac ph\u1ed5 bi\u1ebfn \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng cho c\u00e1c ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u l\u00e0 B-Tree (C\u00e2y c\u00e2n b\u1eb1ng), m\u1eb7c d\u00f9 c\u00e1c c\u1ea5u tr\u00fac kh\u00e1c nh\u01b0 Hash, R-Tree, Bitmap, v.v., t\u00f9y thu\u1ed9c v\u00e0o DBMS v\u00e0 b\u1ea3n ch\u1ea5t c\u1ee7a d\u1eef li\u1ec7u.<\/p>\n<p>Ch\u1ec9 m\u1ee5c B-Tree l\u00e0 c\u1ea5u tr\u00fac d\u1eef li\u1ec7u c\u00e2n b\u1eb1ng, t\u1ef1 s\u1eafp x\u1ebfp, duy tr\u00ec d\u1eef li\u1ec7u \u0111\u00e3 s\u1eafp x\u1ebfp v\u00e0 cho ph\u00e9p th\u1ef1c hi\u1ec7n c\u00e1c thao t\u00e1c ch\u00e8n, x\u00f3a v\u00e0 t\u00ecm ki\u1ebfm hi\u1ec7u qu\u1ea3. \u201cG\u1ed1c\u201d c\u1ee7a C\u00e2y B ch\u1ee9a c\u00e1c con tr\u1ecf t\u1edbi c\u00e1c n\u00fat \u201ccon\u201d, c\u00e1c n\u00fat n\u00e0y c\u00f2n ch\u1ee9a c\u00e1c con tr\u1ecf t\u1edbi c\u00e1c n\u00fat \u201ccon\u201d t\u01b0\u01a1ng \u1ee9ng c\u1ee7a ch\u00fang, t\u1ea1o th\u00e0nh m\u1ed9t c\u1ea5u tr\u00fac gi\u1ed1ng nh\u01b0 c\u00e2y.<\/p>\n<p>Khi DBMS c\u1ea7n t\u00ecm m\u1ed9t b\u1ea3n ghi c\u1ee5 th\u1ec3, n\u00f3 s\u1ebd b\u1eaft \u0111\u1ea7u t\u1ea1i n\u00fat g\u1ed1c c\u1ee7a C\u00e2y B v\u00e0 \u0111i\u1ec1u h\u01b0\u1edbng xu\u1ed1ng c\u00e1c n\u00fat con cho \u0111\u1ebfn khi t\u00ecm th\u1ea5y b\u1ea3n ghi mong mu\u1ed1n. Vi\u1ec7c n\u00e0y nhanh h\u01a1n nhi\u1ec1u so v\u1edbi vi\u1ec7c qu\u00e9t t\u1eebng h\u00e0ng trong b\u1ea3ng.<\/p>\n<h2>C\u00e1c t\u00ednh n\u0103ng ch\u00ednh c\u1ee7a ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/h2>\n<p>M\u1ed9t s\u1ed1 t\u00ednh n\u0103ng n\u1ed5i b\u1eadt c\u1ee7a ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u bao g\u1ed3m:<\/p>\n<ol>\n<li><strong>C\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t:<\/strong> C\u00e1c ch\u1ec9 m\u1ee5c c\u1ea3i thi\u1ec7n \u0111\u00e1ng k\u1ec3 t\u1ed1c \u0111\u1ed9 c\u1ee7a c\u00e1c ho\u1ea1t \u0111\u1ed9ng truy xu\u1ea5t d\u1eef li\u1ec7u.<\/li>\n<li><strong>K\u1ebft c\u1ea5u:<\/strong> Ch\u00fang th\u01b0\u1eddng s\u1eed d\u1ee5ng c\u00e1c c\u1ea5u tr\u00fac d\u1ef1a tr\u00ean c\u00e2y (nh\u01b0 B-Tree ho\u1eb7c B+Tree), nh\u01b0ng c\u00e1c lo\u1ea1i kh\u00e1c nh\u01b0 Hash, Bitmap, v.v., c\u0169ng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng.<\/li>\n<li><strong>Kho:<\/strong> Ch\u00fang l\u01b0u tr\u1eef m\u1ed9t t\u1eadp h\u1ee3p con d\u1eef li\u1ec7u t\u1eeb c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 m\u1ed9t con tr\u1ecf t\u1edbi v\u1ecb tr\u00ed c\u1ee7a t\u1eebng ph\u1ea7n d\u1eef li\u1ec7u.<\/li>\n<li><strong>S\u1ef1 \u0111\u00e1nh \u0111\u1ed5i:<\/strong> Trong khi c\u1ea3i thi\u1ec7n ho\u1ea1t \u0111\u1ed9ng \u0111\u1ecdc, c\u00e1c ch\u1ec9 m\u1ee5c c\u00f3 th\u1ec3 l\u00e0m ch\u1eadm ho\u1ea1t \u0111\u1ed9ng ghi v\u00ec m\u1ed7i s\u1eeda \u0111\u1ed5i tr\u00ean b\u1ea3ng \u0111\u1ec1u y\u00eau c\u1ea7u nh\u1eefng thay \u0111\u1ed5i t\u01b0\u01a1ng \u1ee9ng trong ch\u1ec9 m\u1ee5c.<\/li>\n<li><strong>C\u00e1c lo\u1ea1i:<\/strong> C\u00e1c ch\u1ec9 m\u1ee5c c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c ph\u00e2n c\u1ee5m ho\u1eb7c kh\u00f4ng ph\u00e2n c\u1ee5m, m\u1ed7i ch\u1ec9 m\u1ee5c c\u00f3 c\u00e1c \u0111\u1eb7c \u0111i\u1ec3m v\u00e0 c\u00e1ch s\u1eed d\u1ee5ng ri\u00eang bi\u1ec7t.<\/li>\n<\/ol>\n<h2>C\u00e1c lo\u1ea1i ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/h2>\n<p>Ch\u1ee7 y\u1ebfu c\u00f3 hai lo\u1ea1i ch\u1ec9 m\u1ee5c:<\/p>\n<table>\n<thead>\n<tr>\n<th><strong>Lo\u1ea1i ch\u1ec9 m\u1ee5c<\/strong><\/th>\n<th><strong>S\u1ef1 mi\u00eau t\u1ea3<\/strong><\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Ch\u1ec9 m\u1ee5c c\u1ee5m<\/td>\n<td>Ch\u1ec9 m\u1ee5c \u0111\u01b0\u1ee3c nh\u00f3m x\u00e1c \u0111\u1ecbnh th\u1ee9 t\u1ef1 v\u1eadt l\u00fd c\u1ee7a d\u1eef li\u1ec7u trong b\u1ea3ng. Do \u0111\u00f3, m\u1ed9t b\u1ea3ng ch\u1ec9 c\u00f3 th\u1ec3 c\u00f3 m\u1ed9t ch\u1ec9 m\u1ee5c \u0111\u01b0\u1ee3c nh\u00f3m.<\/td>\n<\/tr>\n<tr>\n<td>Ch\u1ec9 m\u1ee5c kh\u00f4ng ph\u00e2n c\u1ee5m<\/td>\n<td>Ch\u1ec9 m\u1ee5c kh\u00f4ng \u0111\u01b0\u1ee3c nh\u00f3m kh\u00f4ng x\u00e1c \u0111\u1ecbnh th\u1ee9 t\u1ef1 v\u1eadt l\u00fd c\u1ee7a d\u1eef li\u1ec7u trong b\u1ea3ng. Thay v\u00e0o \u0111\u00f3, n\u00f3 s\u1eed d\u1ee5ng m\u1ed9t con tr\u1ecf \u0111\u1ec3 \u0111\u1ecbnh v\u1ecb d\u1eef li\u1ec7u. M\u1ed9t b\u1ea3ng c\u00f3 th\u1ec3 c\u00f3 nhi\u1ec1u ch\u1ec9 m\u1ee5c kh\u00f4ng \u0111\u01b0\u1ee3c nh\u00f3m.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>M\u1ed9t s\u1ed1 lo\u1ea1i ch\u1ec9 m\u1ee5c kh\u00e1c l\u00e0:<\/p>\n<ol>\n<li><strong>Ch\u1ec9 s\u1ed1 duy nh\u1ea5t:<\/strong> \u0110\u1ea3m b\u1ea3o d\u1eef li\u1ec7u trong c\u1ed9t \u0111\u01b0\u1ee3c l\u1eadp ch\u1ec9 m\u1ee5c l\u00e0 duy nh\u1ea5t.<\/li>\n<li><strong>Ch\u1ec9 s\u1ed1 t\u1ed5ng h\u1ee3p:<\/strong> S\u1eed d\u1ee5ng nhi\u1ec1u c\u1ed9t cho ch\u1ec9 m\u1ee5c.<\/li>\n<li><strong>Ch\u1ec9 s\u1ed1 bitmap:<\/strong> L\u00fd t\u01b0\u1edfng cho c\u00e1c c\u1ed9t c\u00f3 s\u1ed1 l\u01b0\u1ee3ng nh\u1ecf c\u00e1c gi\u00e1 tr\u1ecb ri\u00eang bi\u1ec7t (l\u01b0\u1ee3ng s\u1ed1 th\u1ea5p).<\/li>\n<li><strong>Ch\u1ec9 m\u1ee5c to\u00e0n v\u0103n:<\/strong> \u0110\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 t\u00ecm ki\u1ebfm to\u00e0n v\u0103n.<\/li>\n<li><strong>Ch\u1ec9 s\u1ed1 kh\u00f4ng gian:<\/strong> \u0110\u01b0\u1ee3c s\u1eed d\u1ee5ng cho c\u00e1c ki\u1ec3u d\u1eef li\u1ec7u h\u00ecnh h\u1ecdc.<\/li>\n<\/ol>\n<h2>Tri\u1ec3n khai v\u00e0 qu\u1ea3n l\u00fd ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/h2>\n<p>Vi\u1ec7c s\u1eed d\u1ee5ng c\u00e1c ch\u1ec9 m\u1ee5c tuy mang l\u1ea1i l\u1ee3i \u00edch nh\u01b0ng \u0111\u00f2i h\u1ecfi ph\u1ea3i c\u00f3 s\u1ef1 qu\u1ea3n l\u00fd c\u1ea9n th\u1eadn. L\u1eadp ch\u1ec9 m\u1ee5c qu\u00e1 m\u1ee9c c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn thao t\u00e1c ghi ch\u1eadm h\u01a1n v\u00e0 l\u00e3ng ph\u00ed dung l\u01b0\u1ee3ng l\u01b0u tr\u1eef. M\u1eb7t kh\u00e1c, vi\u1ec7c l\u1eadp ch\u1ec9 m\u1ee5c d\u01b0\u1edbi m\u1ee9c c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn ho\u1ea1t \u0111\u1ed9ng \u0111\u1ecdc ch\u1eadm h\u01a1n.<\/p>\n<p>Gi\u00e1m s\u00e1t hi\u1ec7u su\u1ea5t c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a b\u1ea1n v\u00e0 th\u01b0\u1eddng xuy\u00ean c\u1eadp nh\u1eadt chi\u1ebfn l\u01b0\u1ee3c l\u1eadp ch\u1ec9 m\u1ee5c cho ph\u00f9 h\u1ee3p v\u1edbi nhu c\u1ea7u hi\u1ec7n t\u1ea1i c\u1ee7a c\u01a1 s\u1edf d\u1eef li\u1ec7u l\u00e0 r\u1ea5t quan tr\u1ecdng. Ngo\u00e0i ra, vi\u1ec7c ch\u1ecdn \u0111\u00fang lo\u1ea1i ch\u1ec9 m\u1ee5c d\u1ef1a tr\u00ean b\u1ea3n ch\u1ea5t c\u1ee7a d\u1eef li\u1ec7u v\u00e0 c\u00e1c thao t\u00e1c \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n tr\u00ean \u0111\u00f3 \u0111\u00f3ng m\u1ed9t vai tr\u00f2 quan tr\u1ecdng trong vi\u1ec7c tri\u1ec3n khai ch\u1ec9 m\u1ee5c hi\u1ec7u qu\u1ea3.<\/p>\n<h2>So s\u00e1nh ch\u1ec9 m\u1ee5c v\u00e0 \u0111\u1eb7c \u0111i\u1ec3m c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/h2>\n<p>D\u01b0\u1edbi \u0111\u00e2y l\u00e0 b\u1ea3ng so s\u00e1nh c\u00e1c lo\u1ea1i ch\u1ec9 m\u1ee5c kh\u00e1c nhau:<\/p>\n<table>\n<thead>\n<tr>\n<th><strong>Lo\u1ea1i ch\u1ec9 m\u1ee5c<\/strong><\/th>\n<th><strong>T\u0103ng t\u1ed1c ho\u1ea1t \u0111\u1ed9ng \u0111\u1ecdc<\/strong><\/th>\n<th><strong>L\u00e0m ch\u1eadm ho\u1ea1t \u0111\u1ed9ng ghi<\/strong><\/th>\n<th><strong>Y\u00eau c\u1ea7u kh\u00f4ng gian<\/strong><\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>\u0110\u01b0\u1ee3c nh\u00f3m l\u1ea1i<\/td>\n<td>\u0110\u00fang<\/td>\n<td>\u0110\u00fang<\/td>\n<td>V\u1eeba ph\u1ea3i<\/td>\n<\/tr>\n<tr>\n<td>Kh\u00f4ng ph\u00e2n c\u1ee5m<\/td>\n<td>\u0110\u00fang<\/td>\n<td>\u0110\u00fang<\/td>\n<td>Cao<\/td>\n<\/tr>\n<tr>\n<td>B\u1ea3n \u0111\u1ed3 bit<\/td>\n<td>C\u00f3 (s\u1ed1 l\u01b0\u1ee3ng th\u1ebb th\u1ea5p)<\/td>\n<td>\u0110\u00fang<\/td>\n<td>Th\u1ea5p<\/td>\n<\/tr>\n<tr>\n<td>To\u00e0n v\u0103n<\/td>\n<td>C\u00f3 (t\u00ecm ki\u1ebfm v\u0103n b\u1ea3n)<\/td>\n<td>\u0110\u00fang<\/td>\n<td>Cao<\/td>\n<\/tr>\n<tr>\n<td>kh\u00f4ng gian<\/td>\n<td>C\u00f3 (d\u1eef li\u1ec7u h\u00ecnh h\u1ecdc)<\/td>\n<td>\u0110\u00fang<\/td>\n<td>Cao<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Quan \u0111i\u1ec3m v\u00e0 c\u00f4ng ngh\u1ec7 t\u01b0\u01a1ng lai trong l\u1eadp ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/h2>\n<p>T\u01b0\u01a1ng lai c\u1ee7a vi\u1ec7c l\u1eadp ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u n\u1eb1m \u1edf c\u00e1c h\u1ec7 th\u1ed1ng t\u1ef1 \u0111\u1ed9ng h\u00f3a v\u00e0 th\u00edch \u1ee9ng h\u01a1n. C\u00e1c k\u1ef9 thu\u1eadt m\u00e1y h\u1ecdc v\u00e0 AI \u0111ang \u0111\u01b0\u1ee3c ph\u00e1t tri\u1ec3n \u0111\u1ec3 t\u1ef1 \u0111\u1ed9ng qu\u1ea3n l\u00fd v\u00e0 t\u1ed1i \u01b0u h\u00f3a c\u00e1c ch\u1ec9 m\u1ee5c d\u1ef1a tr\u00ean vi\u1ec7c thay \u0111\u1ed5i m\u00f4 h\u00ecnh kh\u1ed1i l\u01b0\u1ee3ng c\u00f4ng vi\u1ec7c.<\/p>\n<p>Ngo\u00e0i ra, v\u1edbi s\u1ef1 gia t\u0103ng c\u1ee7a c\u01a1 s\u1edf d\u1eef li\u1ec7u phi quan h\u1ec7 (NoSQL), c\u00e1c chi\u1ebfn l\u01b0\u1ee3c v\u00e0 c\u1ea5u tr\u00fac l\u1eadp ch\u1ec9 m\u1ee5c kh\u00e1c nhau \u0111ang \u0111\u01b0\u1ee3c ph\u00e1t tri\u1ec3n. V\u00ed d\u1ee5: trong c\u01a1 s\u1edf d\u1eef li\u1ec7u \u0110\u1ed3 th\u1ecb, t\u00ednh k\u1ec1 c\u1eadn kh\u00f4ng c\u00f3 ch\u1ec9 m\u1ee5c c\u00f3 ngh\u0129a l\u00e0 m\u1ecdi ph\u1ea7n t\u1eed \u0111\u1ec1u ch\u1ee9a m\u1ed9t con tr\u1ecf tr\u1ef1c ti\u1ebfp t\u1edbi ph\u1ea7n t\u1eed li\u1ec1n k\u1ec1 c\u1ee7a n\u00f3.<\/p>\n<h2>Ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 m\u00e1y ch\u1ee7 proxy<\/h2>\n<p>M\u1eb7c d\u00f9 m\u00e1y ch\u1ee7 proxy kh\u00f4ng t\u01b0\u01a1ng t\u00e1c tr\u1ef1c ti\u1ebfp v\u1edbi c\u00e1c ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u nh\u01b0ng ch\u00fang \u0111\u00f3ng m\u1ed9t vai tr\u00f2 quan tr\u1ecdng trong vi\u1ec7c c\u00e2n b\u1eb1ng t\u1ea3i v\u00e0 b\u1ed9 \u0111\u1ec7m, \u0111i\u1ec1u n\u00e0y t\u00e1c \u0111\u1ed9ng gi\u00e1n ti\u1ebfp \u0111\u1ebfn hi\u1ec7u su\u1ea5t c\u1ee7a c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/p>\n<p>Khi s\u1eed d\u1ee5ng m\u00e1y ch\u1ee7 proxy, n\u00f3 c\u00f3 th\u1ec3 l\u01b0u v\u00e0o b\u1ed9 nh\u1edb \u0111\u1ec7m c\u00e1c ph\u1ea3n h\u1ed3i t\u1eeb c\u01a1 s\u1edf d\u1eef li\u1ec7u. N\u1ebfu y\u00eau c\u1ea7u t\u01b0\u01a1ng t\u1ef1 \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n l\u1ea1i, proxy c\u00f3 th\u1ec3 tr\u1ea3 v\u1ec1 ph\u1ea3n h\u1ed3i \u0111\u01b0\u1ee3c l\u01b0u trong b\u1ed9 nh\u1edb \u0111\u1ec7m, gi\u1ea3m t\u1ea3i cho c\u01a1 s\u1edf d\u1eef li\u1ec7u. \u0110i\u1ec1u n\u00e0y gi\u00e1n ti\u1ebfp gi\u00fap s\u1eed d\u1ee5ng t\u1ed1t h\u01a1n c\u00e1c t\u00e0i nguy\u00ean c\u01a1 s\u1edf d\u1eef li\u1ec7u, bao g\u1ed3m c\u1ea3 c\u00e1c ch\u1ec9 m\u1ee5c.<\/p>\n<p>H\u01a1n n\u1eefa, trong m\u00f4i tr\u01b0\u1eddng DBMS n\u01a1i nhi\u1ec1u m\u00e1y ch\u1ee7 c\u01a1 s\u1edf d\u1eef li\u1ec7u \u0111ang \u0111\u01b0\u1ee3c qu\u1ea3n l\u00fd, m\u00e1y ch\u1ee7 proxy c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 ph\u00e2n ph\u1ed1i t\u1ea3i, \u0111\u1ea3m b\u1ea3o s\u1eed d\u1ee5ng hi\u1ec7u qu\u1ea3 t\u1ea5t c\u1ea3 c\u00e1c t\u00e0i nguy\u00ean.<\/p>\n<h2>Li\u00ean k\u1ebft li\u00ean quan<\/h2>\n<ul>\n<li><a href=\"https:\/\/en.wikipedia.org\/wiki\/Database_index\" target=\"_new\" rel=\"noopener nofollow\">Gi\u1ea3i th\u00edch v\u1ec1 l\u1eadp ch\u1ec9 m\u1ee5c c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/a><\/li>\n<li><a href=\"https:\/\/www.geeksforgeeks.org\/indexing-in-databases-set-1\/\" target=\"_new\" rel=\"noopener nofollow\">Hi\u1ec3u ch\u1ec9 m\u1ee5c trong c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/a><\/li>\n<li><a href=\"https:\/\/docs.microsoft.com\/en-us\/sql\/relational-databases\/sql-server-index-design-guide?view=sql-server-ver15\" target=\"_new\" rel=\"noopener nofollow\">H\u01b0\u1edbng d\u1eabn thi\u1ebft k\u1ebf v\u00e0 ki\u1ebfn tr\u00fac ch\u1ec9 m\u1ee5c m\u00e1y ch\u1ee7 SQL<\/a><\/li>\n<li><a href=\"https:\/\/dl.acm.org\/doi\/10.5555\/58015\" target=\"_new\" rel=\"noopener nofollow\">L\u1eadp ch\u1ec9 m\u1ee5c v\u00e0 t\u00ecm ki\u1ebfm trong c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/a><\/li>\n<\/ul>","protected":false},"featured_media":468164,"menu_order":0,"template":"","meta":{"_acf_changed":false,"content-type":"","inline_featured_image":false,"footnotes":""},"class_list":["post-476734","wiki","type-wiki","status-publish","has-post-thumbnail","hentry"],"acf":{"faq_title":"Frequently Asked Questions about <mark>Database Index: A Comprehensive Guide<\/mark>","faq_items":[{"question":"What is a database index?","answer":"<p>A database index is a data structure that enhances the speed of data retrieval operations on a database table. It works by storing a subset of the database's data and maintaining a pointer to the location of each piece of data. The index sorts its data based on the indexed columns' values, allowing efficient retrieval.<\/p>"},{"question":"What is the history of database indexes?","answer":"<p>The concept of database indexing emerged along with the development of database management systems. As early as the 1960s, the need for efficient data retrieval methods became apparent. However, it was in the context of the relational database model, proposed by Edgar F. Codd in 1970, that database indexes found their widespread use.<\/p>"},{"question":"How does a database index work?","answer":"<p>A database index works by storing a subset of the database's data and maintaining a pointer to the location of each piece of data. The index sorts its data based on the indexed columns' values, allowing efficient retrieval. When a query is executed, the database engine first scans the index to find the location of the data instead of scanning the entire database table, speeding up data retrieval.<\/p>"},{"question":"What are the key features of a database index?","answer":"<p>Some of the key features of a database index include performance improvement, their structured nature, storage methods, trade-offs (they speed up read operations but slow down write operations), and the two types of indexes: clustered and non-clustered.<\/p>"},{"question":"What are the types of database indexes?","answer":"<p>There are primarily two types of indexes: clustered and non-clustered. A clustered index determines the physical order of data in a table, while a non-clustered index uses a pointer to locate data. Other types of indexes include unique, composite, bitmap, full-text, and spatial indexes.<\/p>"},{"question":"What are the ways to use a database index and what problems may occur?","answer":"<p>The use of indexes significantly speeds up data retrieval operations but requires careful management. Over-indexing can lead to slower write operations and wasted storage space. Under-indexing, on the other hand, can result in slower read operations. It is crucial to monitor the performance of your database and regularly update your indexing strategy.<\/p>"},{"question":"How are database indexes and proxy servers related?","answer":"<p>While proxy servers do not directly interact with database indexes, they do play a significant role in balancing loads and caching, which indirectly impacts the performance of databases. A proxy server can cache responses from a database, reducing the load on the database and helping in better utilizing the database resources, including indexes.<\/p>"},{"question":"What is the future of database indexing?","answer":"<p>The future of database indexing lies in more automated and adaptive systems. Machine learning and AI techniques are being developed to automatically manage and optimize indexes based on changing workload patterns. Also, with the rise of non-relational databases (NoSQL), different indexing strategies and structures are being developed.<\/p>"}]},"_links":{"self":[{"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/wiki\/476734","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/wiki"}],"about":[{"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/types\/wiki"}],"version-history":[{"count":0,"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/wiki\/476734\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/media\/468164"}],"wp:attachment":[{"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/media?parent=476734"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}