{"id":477146,"date":"2023-08-09T09:08:09","date_gmt":"2023-08-09T09:08:09","guid":{"rendered":""},"modified":"2023-09-05T11:14:07","modified_gmt":"2023-09-05T11:14:07","slug":"execution-plan-sql","status":"publish","type":"wiki","link":"https:\/\/oneproxy.pro\/vn\/wiki\/execution-plan-sql\/","title":{"rendered":"K\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n (SQL)"},"content":{"rendered":"

K\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n trong ng\u1eef c\u1ea3nh SQL (Ng\u00f4n ng\u1eef truy v\u1ea5n c\u00f3 c\u1ea5u tr\u00fac) l\u00e0 m\u1ed9t kh\u00eda c\u1ea1nh quan tr\u1ecdng c\u1ee7a vi\u1ec7c t\u1ed1i \u01b0u h\u00f3a hi\u1ec7u su\u1ea5t c\u1ee7a c\u00e1c truy v\u1ea5n c\u01a1 s\u1edf d\u1eef li\u1ec7u. \u0110\u00f3 l\u00e0 m\u1ed9t l\u1ed9 tr\u00ecnh chi ti\u1ebft m\u00e0 h\u1ec7 th\u1ed1ng qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u (DBMS) tu\u00e2n theo \u0111\u1ec3 th\u1ef1c hi\u1ec7n m\u1ed9t truy v\u1ea5n SQL c\u1ee5 th\u1ec3 m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3. K\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n ph\u00e1c th\u1ea3o c\u00e1c b\u01b0\u1edbc v\u00e0 thao t\u00e1c m\u00e0 DBMS s\u1ebd s\u1eed d\u1ee5ng \u0111\u1ec3 truy xu\u1ea5t, n\u1ed1i, l\u1ecdc v\u00e0 x\u1eed l\u00fd d\u1eef li\u1ec7u nh\u1eb1m \u0111\u00e1p \u1ee9ng c\u00e1c y\u00eau c\u1ea7u c\u1ee7a truy v\u1ea5n. Hi\u1ec3u k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n l\u00e0 \u0111i\u1ec1u c\u1ea7n thi\u1ebft \u0111\u1ec3 c\u00e1c qu\u1ea3n tr\u1ecb vi\u00ean v\u00e0 nh\u00e0 ph\u00e1t tri\u1ec3n c\u01a1 s\u1edf d\u1eef li\u1ec7u x\u00e1c \u0111\u1ecbnh v\u00e0 gi\u1ea3i quy\u1ebft c\u00e1c t\u1eafc ngh\u1ebdn v\u1ec1 hi\u1ec7u su\u1ea5t trong \u1ee9ng d\u1ee5ng c\u1ee7a h\u1ecd.<\/p>\n

L\u1ecbch s\u1eed v\u1ec1 ngu\u1ed3n g\u1ed1c c\u1ee7a K\u1ebf ho\u1ea1ch th\u1ef1c thi (SQL) v\u00e0 l\u1ea7n \u0111\u1ea7u ti\u00ean \u0111\u1ec1 c\u1eadp \u0111\u1ebfn n\u00f3<\/h2>\n

Kh\u00e1i ni\u1ec7m v\u1ec1 k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n n\u1ed5i l\u00ean nh\u01b0 m\u1ed9t th\u00e0nh ph\u1ea7n c\u01a1 b\u1ea3n c\u1ee7a h\u1ec7 th\u1ed1ng qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 (RDBMS) v\u00e0o cu\u1ed1i nh\u1eefng n\u0103m 1970 v\u00e0 \u0111\u1ea7u nh\u1eefng n\u0103m 1980. N\u00f3 ph\u00e1t tri\u1ec3n nh\u01b0 m\u1ed9t ph\u1ea3n \u1ee9ng tr\u01b0\u1edbc s\u1ef1 ph\u1ee9c t\u1ea1p ng\u00e0y c\u00e0ng t\u0103ng c\u1ee7a c\u00e1c truy v\u1ea5n c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 nhu c\u1ea7u t\u1ed1i \u01b0u h\u00f3a vi\u1ec7c th\u1ef1c thi ch\u00fang \u0111\u1ec3 c\u00f3 hi\u1ec7u su\u1ea5t t\u1ed1t h\u01a1n.<\/p>\n

M\u1ed9t trong nh\u1eefng \u0111\u1ec1 c\u1eadp s\u1edbm nh\u1ea5t v\u1ec1 k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n c\u00f3 th\u1ec3 b\u1eaft ngu\u1ed3n t\u1eeb s\u1ef1 ph\u00e1t tri\u1ec3n c\u1ee7a d\u1ef1 \u00e1n System R t\u1ea1i IBM Research v\u00e0o \u0111\u1ea7u nh\u1eefng n\u0103m 1970. System R l\u00e0 RDBMS ti\u00ean phong \u0111\u1eb7t n\u1ec1n m\u00f3ng cho nhi\u1ec1u h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u d\u1ef1a tr\u00ean SQL hi\u1ec7n \u0111\u1ea1i. C\u00e1c nh\u00e0 nghi\u00ean c\u1ee9u t\u1ea1i IBM \u0111\u00e3 nh\u1eadn ra t\u1ea7m quan tr\u1ecdng c\u1ee7a vi\u1ec7c th\u1ef1c hi\u1ec7n c\u00e1c truy v\u1ea5n m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3 v\u00e0 \u0111\u00e3 ngh\u0129 ra c\u00e1c k\u1ef9 thu\u1eadt \u0111\u1ec3 t\u1ef1 \u0111\u1ed9ng t\u1ea1o ra c\u00e1c k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n.<\/p>\n

Th\u00f4ng tin chi ti\u1ebft v\u1ec1 K\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n (SQL)<\/h2>\n

M\u1ee5c \u0111\u00edch ch\u00ednh c\u1ee7a k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n l\u00e0 cung c\u1ea5p h\u01b0\u1edbng d\u1eabn t\u1eebng b\u01b0\u1edbc cho c\u00f4ng c\u1ee5 c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u1ec1 c\u00e1ch truy c\u1eadp v\u00e0 thao t\u00e1c d\u1eef li\u1ec7u \u0111\u1ec3 t\u1ea1o ra k\u1ebft qu\u1ea3 truy v\u1ea5n mong mu\u1ed1n. C\u00f4ng c\u1ee5 c\u01a1 s\u1edf d\u1eef li\u1ec7u s\u1eed d\u1ee5ng nhi\u1ec1u thu\u1eadt to\u00e1n, ph\u01b0\u01a1ng ph\u00e1p truy c\u1eadp v\u00e0 chi\u1ebfn l\u01b0\u1ee3c t\u1ed1i \u01b0u h\u00f3a kh\u00e1c nhau \u0111\u1ec3 th\u1ef1c hi\u1ec7n vi\u1ec7c n\u00e0y m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3.<\/p>\n

Khi m\u1ed9t truy v\u1ea5n \u0111\u01b0\u1ee3c g\u1eedi t\u1edbi DBMS, n\u00f3 s\u1ebd tr\u1ea3i qua m\u1ed9t quy tr\u00ecnh g\u1ed3m nhi\u1ec1u b\u01b0\u1edbc tr\u01b0\u1edbc khi vi\u1ec7c truy xu\u1ea5t v\u00e0 x\u1eed l\u00fd d\u1eef li\u1ec7u th\u1ef1c t\u1ebf c\u00f3 th\u1ec3 di\u1ec5n ra. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 t\u1ed5ng quan v\u1ec1 qu\u00e1 tr\u00ecnh:<\/p>\n

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    Ph\u00e2n t\u00edch c\u00fa ph\u00e1p:<\/strong> DBMS tr\u01b0\u1edbc ti\u00ean ph\u00e2n t\u00edch c\u00fa ph\u00e1p truy v\u1ea5n SQL \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o t\u00ednh ch\u00ednh x\u00e1c v\u1ec1 c\u00fa ph\u00e1p v\u00e0 ng\u1eef ngh\u0129a c\u1ee7a n\u00f3. N\u00f3 ki\u1ec3m tra t\u00ean b\u1ea3ng v\u00e0 c\u1ed9t th\u00edch h\u1ee3p, c\u00fa ph\u00e1p \u0111\u00fang v\u00e0 c\u00e1c tham chi\u1ebfu h\u1ee3p l\u1ec7.<\/p>\n<\/li>\n

  2. \n

    T\u1ed1i \u01b0u h\u00f3a:<\/strong> Khi truy v\u1ea5n \u0111\u01b0\u1ee3c x\u00e1c th\u1ef1c, tr\u00ecnh t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n s\u1ebd ho\u1ea1t \u0111\u1ed9ng. Tr\u00ecnh t\u1ed1i \u01b0u h\u00f3a kh\u00e1m ph\u00e1 c\u00e1c k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n kh\u00e1c nhau v\u00e0 ch\u1ecdn k\u1ebf ho\u1ea1ch hi\u1ec7u qu\u1ea3 nh\u1ea5t. N\u00f3 xem x\u00e9t c\u00e1c y\u1ebfu t\u1ed1 nh\u01b0 ch\u1ec9 m\u1ee5c c\u00f3 s\u1eb5n, s\u1ed1 li\u1ec7u th\u1ed1ng k\u00ea v\u00e0 tr\u1ea1ng th\u00e1i hi\u1ec7n t\u1ea1i c\u1ee7a c\u01a1 s\u1edf d\u1eef li\u1ec7u \u0111\u1ec3 \u0111\u01b0a ra quy\u1ebft \u0111\u1ecbnh s\u00e1ng su\u1ed1t.<\/p>\n<\/li>\n

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    L\u1eadp k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n:<\/strong> Sau khi t\u1ed1i \u01b0u h\u00f3a, k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n \u0111\u00e3 ch\u1ecdn s\u1ebd \u0111\u01b0\u1ee3c t\u1ea1o. K\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n th\u01b0\u1eddng \u0111\u01b0\u1ee3c bi\u1ec3u di\u1ec5n d\u01b0\u1edbi d\u1ea1ng c\u1ea5u tr\u00fac d\u1ea1ng c\u00e2y, v\u1edbi m\u1ed7i n\u00fat bi\u1ec3u th\u1ecb m\u1ed9t thao t\u00e1c (v\u00ed d\u1ee5: qu\u00e9t, n\u1ed1i, s\u1eafp x\u1ebfp) v\u00e0 c\u00e1c k\u1ebft n\u1ed1i gi\u1eefa c\u00e1c n\u00fat bi\u1ec3u th\u1ecb lu\u1ed3ng d\u1eef li\u1ec7u.<\/p>\n<\/li>\n

  4. \n

    Ch\u1ea5p h\u00e0nh:<\/strong> V\u1edbi k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n trong tay, DBMS th\u1ef1c hi\u1ec7n truy v\u1ea5n theo c\u00e1c b\u01b0\u1edbc \u0111\u01b0\u1ee3c n\u00eau trong k\u1ebf ho\u1ea1ch. Trong qu\u00e1 tr\u00ecnh th\u1ef1c thi, c\u00f4ng c\u1ee5 c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng c\u00e1c k\u1ef9 thu\u1eadt kh\u00e1c nhau nh\u01b0 t\u00ecm ki\u1ebfm ch\u1ec9 m\u1ee5c, qu\u00e9t ch\u1ec9 m\u1ee5c, n\u1ed1i b\u0103m, n\u1ed1i v\u00f2ng l\u1eb7p l\u1ed3ng nhau v\u00e0 s\u1eafp x\u1ebfp \u0111\u1ec3 t\u00ecm n\u1ea1p v\u00e0 x\u1eed l\u00fd d\u1eef li\u1ec7u.<\/p>\n<\/li>\n

  5. \n

    Truy xu\u1ea5t k\u1ebft qu\u1ea3:<\/strong> Cu\u1ed1i c\u00f9ng, c\u00f4ng c\u1ee5 truy v\u1ea5n l\u1ea5y k\u1ebft qu\u1ea3 truy v\u1ea5n v\u00e0 hi\u1ec3n th\u1ecb ch\u00fang cho ng\u01b0\u1eddi d\u00f9ng ho\u1eb7c \u1ee9ng d\u1ee5ng.<\/p>\n<\/li>\n<\/ol>\n

    C\u1ea5u tr\u00fac b\u00ean trong c\u1ee7a K\u1ebf ho\u1ea1ch th\u1ef1c thi (SQL) \u2013 C\u00e1ch th\u1ee9c ho\u1ea1t \u0111\u1ed9ng c\u1ee7a K\u1ebf ho\u1ea1ch th\u1ef1c thi (SQL)<\/h2>\n

    C\u1ea5u tr\u00fac b\u00ean trong c\u1ee7a k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n ph\u1ee5 thu\u1ed9c v\u00e0o h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u01a1 b\u1ea3n v\u00e0 tr\u00ecnh t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n c\u1ee7a n\u00f3. Tuy nhi\u00ean, c\u00e1c nguy\u00ean t\u1eafc c\u01a1 b\u1ea3n v\u1eabn nh\u1ea5t qu\u00e1n tr\u00ean h\u1ea7u h\u1ebft c\u00e1c DBMS.<\/p>\n

    K\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n th\u01b0\u1eddng \u0111\u01b0\u1ee3c bi\u1ec3u di\u1ec5n d\u01b0\u1edbi d\u1ea1ng c\u1ea5u tr\u00fac d\u1ea1ng c\u00e2y, trong \u0111\u00f3 m\u1ed7i n\u00fat t\u01b0\u01a1ng \u1ee9ng v\u1edbi m\u1ed9t thao t\u00e1c c\u1ee5 th\u1ec3 v\u00e0 c\u00e1c c\u1ea1nh bi\u1ec3u th\u1ecb lu\u1ed3ng d\u1eef li\u1ec7u gi\u1eefa c\u00e1c thao t\u00e1c. C\u00e1c n\u00fat c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c ph\u00e2n lo\u1ea1i th\u00e0nh nhi\u1ec1u lo\u1ea1i, bao g\u1ed3m:<\/p>\n

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      Qu\u00e9t b\u1ea3ng:<\/strong> N\u00fat n\u00e0y th\u1ec3 hi\u1ec7n qu\u00e1 tr\u00ecnh qu\u00e9t to\u00e0n b\u1ed9 b\u1ea3ng, trong \u0111\u00f3 DBMS \u0111\u1ecdc t\u1ea5t c\u1ea3 c\u00e1c h\u00e0ng t\u1eeb m\u1ed9t b\u1ea3ng \u0111\u1ec3 t\u00ecm d\u1eef li\u1ec7u c\u1ea7n thi\u1ebft.<\/p>\n<\/li>\n

    2. \n

      Qu\u00e9t\/T\u00ecm ki\u1ebfm ch\u1ec9 m\u1ee5c:<\/strong> C\u00e1c n\u00fat n\u00e0y t\u01b0\u01a1ng \u1ee9ng v\u1edbi vi\u1ec7c truy c\u1eadp d\u1eef li\u1ec7u b\u1eb1ng ch\u1ec9 m\u1ee5c. Qu\u00e9t ch\u1ec9 m\u1ee5c bao g\u1ed3m vi\u1ec7c \u0111\u1ecdc c\u00e1c m\u1ee5c nh\u1eadp ch\u1ec9 m\u1ee5c v\u00e0 sau \u0111\u00f3 t\u00ecm n\u1ea1p c\u00e1c h\u00e0ng t\u01b0\u01a1ng \u1ee9ng t\u1eeb b\u1ea3ng, trong khi t\u00ecm ki\u1ebfm ch\u1ec9 m\u1ee5c s\u1ebd tr\u1ef1c ti\u1ebfp \u0111\u1ecbnh v\u1ecb c\u00e1c h\u00e0ng b\u1eb1ng ch\u1ec9 m\u1ee5c.<\/p>\n<\/li>\n

    3. \n

      L\u1ecdc:<\/strong> N\u00fat b\u1ed9 l\u1ecdc \u00e1p d\u1ee5ng m\u1ed9t v\u1ecb t\u1eeb \u0111\u1ec3 l\u1ecdc c\u00e1c h\u00e0ng d\u1ef1a tr\u00ean c\u00e1c \u0111i\u1ec1u ki\u1ec7n \u0111\u00e3 ch\u1ec9 \u0111\u1ecbnh.<\/p>\n<\/li>\n

    4. \n

      Lo\u1ea1i:<\/strong> N\u00fat s\u1eafp x\u1ebfp ch\u1ecbu tr\u00e1ch nhi\u1ec7m s\u1eafp x\u1ebfp d\u1eef li\u1ec7u d\u1ef1a tr\u00ean c\u00e1c c\u1ed9t \u0111\u01b0\u1ee3c ch\u1ec9 \u0111\u1ecbnh.<\/p>\n<\/li>\n

    5. \n

      Tham gia:<\/strong> C\u00e1c n\u00fat tham gia x\u1eed l\u00fd vi\u1ec7c k\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb nhi\u1ec1u b\u1ea3ng d\u1ef1a tr\u00ean c\u00e1c \u0111i\u1ec1u ki\u1ec7n tham gia.<\/p>\n<\/li>\n<\/ol>\n

      Tr\u00ecnh t\u1ed1i \u01b0u h\u00f3a c\u01a1 s\u1edf d\u1eef li\u1ec7u \u0111\u00e1nh gi\u00e1 c\u00e1c k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n kh\u00e1c nhau v\u00e0 \u1ea5n \u0111\u1ecbnh chi ph\u00ed cho m\u1ed7i k\u1ebf ho\u1ea1ch. Ph\u01b0\u01a1ng \u00e1n c\u00f3 chi ph\u00ed th\u1ea5p nh\u1ea5t \u0111\u01b0\u1ee3c ch\u1ecdn l\u00e0 ph\u01b0\u01a1ng \u00e1n t\u1ed1i \u01b0u v\u00e0 \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n \u0111\u1ec3 ho\u00e0n th\u00e0nh truy v\u1ea5n.<\/p>\n

      Ph\u00e2n t\u00edch c\u00e1c t\u00ednh n\u0103ng ch\u00ednh c\u1ee7a K\u1ebf ho\u1ea1ch th\u1ef1c thi (SQL)<\/h2>\n

      C\u00e1c t\u00ednh n\u0103ng ch\u00ednh c\u1ee7a k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n trong SQL l\u00e0:<\/p>\n

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        T\u1ed1i \u01b0u h\u00f3a:<\/strong> K\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n t\u1eadn d\u1ee5ng tr\u00ecnh t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n, gi\u00fap kh\u00e1m ph\u00e1 nhi\u1ec1u chi\u1ebfn l\u01b0\u1ee3c nh\u1eb1m x\u00e1c \u0111\u1ecbnh c\u00e1ch hi\u1ec7u qu\u1ea3 nh\u1ea5t \u0111\u1ec3 th\u1ef1c hi\u1ec7n truy v\u1ea5n. N\u00f3 t\u00ednh \u0111\u1ebfn c\u00e1c y\u1ebfu t\u1ed1 nh\u01b0 ch\u1ec9 m\u1ee5c, s\u1ed1 li\u1ec7u th\u1ed1ng k\u00ea v\u00e0 k\u00edch th\u01b0\u1edbc b\u1ea3ng c\u00f3 s\u1eb5n \u0111\u1ec3 \u01b0\u1edbc t\u00ednh chi ph\u00ed c\u1ee7a t\u1eebng g\u00f3i.<\/p>\n<\/li>\n

      2. \n

        Uy\u1ec3n chuy\u1ec3n:<\/strong> T\u00f9y thu\u1ed9c v\u00e0o h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u, k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n c\u00f3 th\u1ec3 b\u1ecb \u1ea3nh h\u01b0\u1edfng ho\u1eb7c th\u1eadm ch\u00ed \u0111\u01b0\u1ee3c th\u1ef1c thi b\u1edfi nh\u00e0 ph\u00e1t tri\u1ec3n. \u0110i\u1ec1u n\u00e0y c\u00f3 th\u1ec3 \u0111\u1ea1t \u0111\u01b0\u1ee3c th\u00f4ng qua vi\u1ec7c s\u1eed d\u1ee5ng c\u00e1c g\u1ee3i \u00fd ho\u1eb7c ch\u1ec9 th\u1ecb \u0111\u01b0\u1ee3c nh\u00fang trong truy v\u1ea5n SQL.<\/p>\n<\/li>\n

      3. \n

        T\u1ed1i \u01b0u h\u00f3a \u0111\u1ed9ng:<\/strong> M\u1ed9t s\u1ed1 DBMS hi\u1ec7n \u0111\u1ea1i h\u1ed7 tr\u1ee3 t\u1ed1i \u01b0u h\u00f3a \u0111\u1ed9ng, trong \u0111\u00f3 k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n c\u00f3 th\u1ec3 thay \u0111\u1ed5i trong qu\u00e1 tr\u00ecnh th\u1ef1c hi\u1ec7n truy v\u1ea5n d\u1ef1a tr\u00ean vi\u1ec7c ph\u00e2n ph\u1ed1i d\u1eef li\u1ec7u th\u1ef1c t\u1ebf v\u00e0 t\u00ednh s\u1eb5n c\u00f3 c\u1ee7a t\u00e0i nguy\u00ean.<\/p>\n<\/li>\n

      4. \n

        Quy\u1ebft \u0111\u1ecbnh d\u1ef1a tr\u00ean th\u1ed1ng k\u00ea:<\/strong> Tr\u00ecnh t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n ch\u1ee7 y\u1ebfu d\u1ef1a v\u00e0o s\u1ed1 li\u1ec7u th\u1ed1ng k\u00ea v\u1ec1 c\u00e1c b\u1ea3ng v\u00e0 ch\u1ec9 m\u1ee5c trong c\u01a1 s\u1edf d\u1eef li\u1ec7u \u0111\u1ec3 \u0111\u01b0a ra quy\u1ebft \u0111\u1ecbnh s\u00e1ng su\u1ed1t v\u1ec1 k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n hi\u1ec7u qu\u1ea3 nh\u1ea5t.<\/p>\n<\/li>\n<\/ol>\n

        C\u00e1c lo\u1ea1i k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n (SQL)<\/h2>\n

        C\u00f3 m\u1ed9t s\u1ed1 lo\u1ea1i k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n m\u00e0 tr\u00ecnh t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n c\u00f3 th\u1ec3 xem x\u00e9t d\u1ef1a tr\u00ean \u0111\u1ed9 ph\u1ee9c t\u1ea1p c\u1ee7a truy v\u1ea5n, ph\u00e2n ph\u1ed1i d\u1eef li\u1ec7u v\u00e0 t\u00e0i nguy\u00ean s\u1eb5n c\u00f3. C\u00e1c lo\u1ea1i ph\u1ed5 bi\u1ebfn nh\u1ea5t bao g\u1ed3m:<\/p>\n

          \n
        1. \n

          K\u1ebf ho\u1ea1ch qu\u00e9t b\u1ea3ng:<\/strong> K\u1ebf ho\u1ea1ch n\u00e0y bao g\u1ed3m vi\u1ec7c qu\u00e9t to\u00e0n b\u1ed9 b\u1ea3ng \u0111\u1ec3 l\u1ea5y d\u1eef li\u1ec7u c\u1ea7n thi\u1ebft. N\u00f3 ph\u00f9 h\u1ee3p v\u1edbi c\u00e1c b\u1ea3ng nh\u1ecf ho\u1eb7c khi c\u1ea7n truy c\u1eadp m\u1ed9t ph\u1ea7n \u0111\u00e1ng k\u1ec3 c\u1ee7a b\u1ea3ng.<\/p>\n<\/li>\n

        2. \n

          K\u1ebf ho\u1ea1ch qu\u00e9t ch\u1ec9 m\u1ee5c:<\/strong> Trong k\u1ebf ho\u1ea1ch n\u00e0y, tr\u00ecnh t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n s\u1eed d\u1ee5ng ch\u1ec9 m\u1ee5c \u0111\u1ec3 \u0111\u1ecbnh v\u1ecb c\u00e1c h\u00e0ng mong mu\u1ed1n m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3. N\u00f3 ho\u1ea1t \u0111\u1ed9ng t\u1ed1t khi ch\u1ec9 m\u1ee5c c\u00f3 t\u00ednh ch\u1ecdn l\u1ecdc cao v\u00e0 ch\u1ec9 c\u1ea7n truy c\u1eadp m\u1ed9t t\u1eadp h\u1ee3p con nh\u1ecf c\u00e1c h\u00e0ng.<\/p>\n<\/li>\n

        3. \n

          K\u1ebf ho\u1ea1ch tham gia v\u00f2ng l\u1eb7p l\u1ed3ng nhau:<\/strong> K\u1ebf ho\u1ea1ch n\u00e0y bao g\u1ed3m vi\u1ec7c l\u1eb7p qua m\u1ed9t b\u1ea3ng v\u00e0 th\u0103m d\u00f2 m\u1ed9t b\u1ea3ng kh\u00e1c \u0111\u1ec3 t\u00ecm c\u00e1c h\u00e0ng kh\u1edbp d\u1ef1a tr\u00ean \u0111i\u1ec1u ki\u1ec7n n\u1ed1i. S\u1ebd hi\u1ec7u qu\u1ea3 khi m\u1ed9t trong c\u00e1c b\u1ea3ng nh\u1ecf v\u00e0 c\u00f3 ch\u1ec9 m\u1ee5c tr\u00ean c\u1ed9t n\u1ed1i.<\/p>\n<\/li>\n

        4. \n

          K\u1ebf ho\u1ea1ch tham gia Hash:<\/strong> Ph\u00e9p n\u1ed1i b\u0103m \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng cho c\u00e1c b\u1ea3ng l\u1edbn h\u01a1n v\u00e0 li\u00ean quan \u0111\u1ebfn vi\u1ec7c x\u00e2y d\u1ef1ng b\u1ea3ng b\u0103m cho m\u1ed9t trong c\u00e1c b\u1ea3ng \u0111\u1ea7u v\u00e0o, sau \u0111\u00f3 th\u0103m d\u00f2 n\u00f3 b\u1eb1ng b\u1ea3ng kh\u00e1c. N\u00f3 hi\u1ec7u qu\u1ea3 cho c\u00e1c k\u1ebft n\u1ed1i quy m\u00f4 l\u1edbn.<\/p>\n<\/li>\n

        5. \n

          K\u1ebf ho\u1ea1ch tham gia h\u1ee3p nh\u1ea5t:<\/strong> Ph\u00e9p n\u1ed1i h\u1ee3p nh\u1ea5t ho\u1ea1t \u0111\u1ed9ng t\u1ed1t khi c\u1ea3 hai b\u1ea3ng \u0111\u1ea7u v\u00e0o \u0111\u01b0\u1ee3c s\u1eafp x\u1ebfp tr\u00ean c\u00e1c c\u1ed9t n\u1ed1i. N\u00f3 h\u1ee3p nh\u1ea5t m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3 c\u00e1c d\u1eef li\u1ec7u \u0111\u00e3 \u0111\u01b0\u1ee3c s\u1eafp x\u1ebfp \u0111\u1ec3 th\u1ef1c hi\u1ec7n ph\u00e9p n\u1ed1i.<\/p>\n<\/li>\n

        6. \n

          K\u1ebf ho\u1ea1ch s\u1eafp x\u1ebfp:<\/strong> K\u1ebf ho\u1ea1ch n\u00e0y s\u1eafp x\u1ebfp d\u1eef li\u1ec7u d\u1ef1a tr\u00ean c\u00e1c c\u1ed9t \u0111\u01b0\u1ee3c ch\u1ec9 \u0111\u1ecbnh. N\u00f3 c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng cho c\u00e1c truy v\u1ea5n ORDER BY ho\u1eb7c \u0111\u1ec3 t\u1ed1i \u01b0u h\u00f3a c\u00e1c ph\u00e9p n\u1ed1i nh\u1ea5t \u0111\u1ecbnh.<\/p>\n<\/li>\n<\/ol>\n

          Lo\u1ea1i k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n \u0111\u01b0\u1ee3c ch\u1ecdn t\u00f9y thu\u1ed9c v\u00e0o nhi\u1ec1u y\u1ebfu t\u1ed1 kh\u00e1c nhau, bao g\u1ed3m c\u1ea5u tr\u00fac truy v\u1ea5n, c\u00e1c ch\u1ec9 m\u1ee5c c\u00f3 s\u1eb5n v\u00e0 k\u00edch th\u01b0\u1edbc c\u1ee7a c\u00e1c b\u1ea3ng li\u00ean quan.<\/p>\n

          C\u00e1c c\u00e1ch s\u1eed d\u1ee5ng K\u1ebf ho\u1ea1ch th\u1ef1c thi (SQL), c\u00e1c v\u1ea5n \u0111\u1ec1 v\u00e0 gi\u1ea3i ph\u00e1p li\u00ean quan \u0111\u1ebfn vi\u1ec7c s\u1eed d\u1ee5ng<\/h2>\n

          C\u00e1c c\u00e1ch s\u1eed d\u1ee5ng K\u1ebf ho\u1ea1ch th\u1ef1c thi (SQL)<\/h3>\n
            \n
          1. \n

            T\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n:<\/strong> M\u1ee5c \u0111\u00edch ch\u00ednh c\u1ee7a k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n l\u00e0 t\u1ed1i \u01b0u h\u00f3a hi\u1ec7u su\u1ea5t truy v\u1ea5n. B\u1eb1ng c\u00e1ch hi\u1ec3u k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n, nh\u00e0 ph\u00e1t tri\u1ec3n v\u00e0 qu\u1ea3n tr\u1ecb vi\u00ean c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u00f3 th\u1ec3 x\u00e1c \u0111\u1ecbnh c\u00e1c truy v\u1ea5n kh\u00f4ng hi\u1ec7u qu\u1ea3 v\u00e0 c\u01a1 c\u1ea5u l\u1ea1i ch\u00fang \u0111\u1ec3 c\u1ea3i thi\u1ec7n th\u1eddi gian th\u1ef1c hi\u1ec7n.<\/p>\n<\/li>\n

          2. \n

            Kh\u1eafc ph\u1ee5c s\u1ef1 c\u1ed1 v\u1ec1 hi\u1ec7u su\u1ea5t:<\/strong> Khi m\u1ed9t truy v\u1ea5n kh\u00f4ng ho\u1ea1t \u0111\u1ed9ng nh\u01b0 mong \u0111\u1ee3i, vi\u1ec7c ki\u1ec3m tra k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n c\u1ee7a n\u00f3 c\u00f3 th\u1ec3 ph\u00e1t hi\u1ec7n ra nh\u1eefng t\u1eafc ngh\u1ebdn ti\u1ec1m \u1ea9n. N\u00f3 cho ph\u00e9p x\u00e1c \u0111\u1ecbnh ch\u00ednh x\u00e1c c\u00e1c v\u1ea5n \u0111\u1ec1 nh\u01b0 thi\u1ebfu ch\u1ec9 m\u1ee5c, chi\u1ebfn l\u01b0\u1ee3c n\u1ed1i kh\u00f4ng \u0111\u00fang ho\u1eb7c s\u1eafp x\u1ebfp qu\u00e1 m\u1ee9c.<\/p>\n<\/li>\n

          3. \n

            Thi\u1ebft k\u1ebf ch\u1ec9 m\u1ee5c:<\/strong> Ph\u00e2n t\u00edch k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n c\u00f3 th\u1ec3 gi\u00fap \u0111\u01b0a ra quy\u1ebft \u0111\u1ecbnh s\u00e1ng su\u1ed1t v\u1ec1 vi\u1ec7c t\u1ea1o ho\u1eb7c s\u1eeda \u0111\u1ed5i ch\u1ec9 m\u1ee5c \u0111\u1ec3 h\u1ed7 tr\u1ee3 th\u1ef1c hi\u1ec7n truy v\u1ea5n t\u1ed1t h\u01a1n.<\/p>\n<\/li>\n<\/ol>\n

            C\u00e1c v\u1ea5n \u0111\u1ec1 v\u00e0 gi\u1ea3i ph\u00e1p li\u00ean quan \u0111\u1ebfn vi\u1ec7c s\u1eed d\u1ee5ng Execution Plan (SQL)<\/h3>\n
              \n
            1. \n

              Th\u1ed1ng k\u00ea b\u1ecb thi\u1ebfu ho\u1eb7c c\u0169:<\/strong> S\u1ed1 li\u1ec7u th\u1ed1ng k\u00ea l\u1ed7i th\u1eddi ho\u1eb7c b\u1ecb thi\u1ebfu c\u00f3 th\u1ec3 \u0111\u00e1nh l\u1eeba tr\u00ecnh t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n, d\u1eabn \u0111\u1ebfn k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n d\u01b0\u1edbi m\u1ee9c t\u1ed1i \u01b0u. Vi\u1ec7c c\u1eadp nh\u1eadt s\u1ed1 li\u1ec7u th\u1ed1ng k\u00ea th\u01b0\u1eddng xuy\u00ean gi\u00fap duy tr\u00ec \u01b0\u1edbc t\u00ednh l\u01b0\u1ee3ng s\u1ed1 ch\u00ednh x\u00e1c, c\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t truy v\u1ea5n.<\/p>\n<\/li>\n

            2. \n

              Chi\u1ebfn l\u01b0\u1ee3c tham gia kh\u00f4ng hi\u1ec7u qu\u1ea3:<\/strong> Trong m\u1ed9t s\u1ed1 tr\u01b0\u1eddng h\u1ee3p, tr\u00ecnh t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n c\u00f3 th\u1ec3 ch\u1ecdn chi\u1ebfn l\u01b0\u1ee3c tham gia kh\u00f4ng ph\u00f9 h\u1ee3p, d\u1eabn \u0111\u1ebfn truy v\u1ea5n ch\u1eadm. Vi\u1ec7c s\u1eed d\u1ee5ng g\u1ee3i \u00fd truy v\u1ea5n ho\u1eb7c c\u01a1 c\u1ea5u l\u1ea1i truy v\u1ea5n c\u00f3 th\u1ec3 h\u01b0\u1edbng d\u1eabn tr\u00ecnh t\u1ed1i \u01b0u h\u00f3a h\u01b0\u1edbng t\u1edbi m\u1ed9t k\u1ebf ho\u1ea1ch t\u1ed1t h\u01a1n.<\/p>\n<\/li>\n

            3. \n

              L\u1ef1a ch\u1ecdn ch\u1ec9 s\u1ed1:<\/strong> Tr\u00ecnh t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n c\u00f3 th\u1ec3 kh\u00f4ng ph\u1ea3i l\u00fac n\u00e0o c\u0169ng ch\u1ecdn ch\u1ec9 m\u1ee5c ph\u00f9 h\u1ee3p nh\u1ea5t cho truy v\u1ea5n. Ch\u1ec9 \u0111\u1ecbnh ch\u1ec9 m\u1ee5c theo c\u00e1ch th\u1ee7 c\u00f4ng ho\u1eb7c s\u1eed d\u1ee5ng g\u1ee3i \u00fd ch\u1ec9 m\u1ee5c c\u00f3 th\u1ec3 c\u00f3 \u00edch trong nh\u1eefng t\u00ecnh hu\u1ed1ng nh\u01b0 v\u1eady.<\/p>\n<\/li>\n

            4. \n

              \u0110\u00e1nh h\u01a1i tham s\u1ed1:<\/strong> Trong tr\u01b0\u1eddng h\u1ee3p c\u00e1c tham s\u1ed1 truy v\u1ea5n r\u1ea5t kh\u00e1c nhau, k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n \u0111\u01b0\u1ee3c t\u1ea1o cho m\u1ed9t b\u1ed9 tham s\u1ed1 c\u00f3 th\u1ec3 kh\u00f4ng t\u1ed1i \u01b0u cho c\u00e1c b\u1ed9 tham s\u1ed1 kh\u00e1c. V\u1ea5n \u0111\u1ec1 n\u00e0y, \u0111\u01b0\u1ee3c g\u1ecdi l\u00e0 \u0111\u00e1nh h\u01a1i tham s\u1ed1, c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c gi\u1ea3i quy\u1ebft b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng c\u00e1c k\u1ef9 thu\u1eadt nh\u01b0 tham s\u1ed1 h\u00f3a truy v\u1ea5n ho\u1eb7c b\u1ed9 nh\u1edb \u0111\u1ec7m k\u1ebf ho\u1ea1ch.<\/p>\n<\/li>\n<\/ol>\n

              C\u00e1c \u0111\u1eb7c \u0111i\u1ec3m ch\u00ednh v\u00e0 so s\u00e1nh kh\u00e1c v\u1edbi c\u00e1c thu\u1eadt ng\u1eef t\u01b0\u01a1ng t\u1ef1 d\u01b0\u1edbi d\u1ea1ng b\u1ea3ng v\u00e0 danh s\u00e1ch<\/h2>\n\n\n\n\n\n\n\n\n\n\n
              T\u00ednh n\u0103ng<\/th>\nK\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n (SQL)<\/th>\nK\u1ebf ho\u1ea1ch truy v\u1ea5n<\/th>\nK\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n (L\u1eadp tr\u00ecnh)<\/th>\n<\/tr>\n<\/thead>\n
              Ki\u1ec3u<\/td>\nTh\u1ef1c hi\u1ec7n truy v\u1ea5n c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/td>\nTh\u1ef1c hi\u1ec7n truy v\u1ea5n c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/td>\nTh\u1ef1c hi\u1ec7n ch\u01b0\u01a1ng tr\u00ecnh<\/td>\n<\/tr>\n
              M\u1ee5c \u0111\u00edch<\/td>\nT\u1ed1i \u01b0u h\u00f3a hi\u1ec7u su\u1ea5t truy v\u1ea5n<\/td>\nT\u1ed1i \u01b0u h\u00f3a hi\u1ec7u su\u1ea5t truy v\u1ea5n<\/td>\nX\u00e1c \u0111\u1ecbnh lu\u1ed3ng ch\u01b0\u01a1ng tr\u00ecnh<\/td>\n<\/tr>\n
              \u0110\u1ed9 chi ti\u1ebft<\/td>\nC\u1ea5p \u0111\u1ed9 truy v\u1ea5n<\/td>\nC\u1ea5p \u0111\u1ed9 truy v\u1ea5n<\/td>\nC\u1ea5p \u0111\u1ed9 kh\u1ed1i l\u1ec7nh ho\u1eb7c m\u00e3<\/td>\n<\/tr>\n
              C\u00e1ch s\u1eed d\u1ee5ng<\/td>\nQu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/td>\nQu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/td>\nPh\u00e1t tri\u1ec3n ph\u1ea7n m\u1ec1m<\/td>\n<\/tr>\n
              \u0111\u1ea1i di\u1ec7n<\/td>\nC\u1ea5u tr\u00fac d\u1ea1ng c\u00e2y<\/td>\nC\u1ea5u tr\u00fac d\u1ea1ng c\u00e2y<\/td>\nS\u01a1 \u0111\u1ed3 lu\u1ed3ng \u0111i\u1ec1u khi\u1ec3n<\/td>\n<\/tr>\n
              Th\u00f4ng tin s\u1eb5n c\u00f3<\/td>\nSi\u00eau d\u1eef li\u1ec7u h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/td>\nSi\u00eau d\u1eef li\u1ec7u h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/td>\nC\u00f3 s\u1eb5n trong th\u1eddi gian ch\u1ea1y<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

              C\u00e1c quan \u0111i\u1ec3m v\u00e0 c\u00f4ng ngh\u1ec7 c\u1ee7a t\u01b0\u01a1ng lai li\u00ean quan \u0111\u1ebfn K\u1ebf ho\u1ea1ch th\u1ef1c thi (SQL)<\/h2>\n

              T\u01b0\u01a1ng lai c\u1ee7a c\u00e1c k\u1ebf ho\u1ea1ch th\u1ef1c thi trong SQL g\u1eafn li\u1ec1n v\u1edbi nh\u1eefng ti\u1ebfn b\u1ed9 trong c\u00f4ng ngh\u1ec7 c\u01a1 s\u1edf d\u1eef li\u1ec7u, \u0111\u1eb7c bi\u1ec7t l\u00e0 trong t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n v\u00e0 h\u1ecdc m\u00e1y. M\u1ed9t s\u1ed1 ph\u00e1t tri\u1ec3n ti\u1ec1m n\u0103ng trong t\u01b0\u01a1ng lai bao g\u1ed3m:<\/p>\n

                \n
              1. \n

                T\u1ed1i \u01b0u h\u00f3a d\u1ef1a tr\u00ean m\u00e1y h\u1ecdc:<\/strong> Khi \u0111\u1ed9 ph\u1ee9c t\u1ea1p c\u1ee7a d\u1eef li\u1ec7u v\u00e0 truy v\u1ea5n ti\u1ebfp t\u1ee5c t\u0103ng, c\u00e1c k\u1ef9 thu\u1eadt h\u1ecdc m\u00e1y c\u00f3 th\u1ec3 \u0111\u01b0\u1ee3c t\u00edch h\u1ee3p v\u00e0o t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n. \u0110i\u1ec1u n\u00e0y c\u00f3 th\u1ec3 d\u1eabn \u0111\u1ebfn c\u00e1c k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n c\u00f3 t\u00ednh th\u00edch \u1ee9ng v\u00e0 nh\u1eadn bi\u1ebft ng\u1eef c\u1ea3nh t\u1ed1t h\u01a1n.<\/p>\n<\/li>\n

              2. \n

                L\u1eadp ch\u1ec9 m\u1ee5c t\u1ef1 \u0111\u1ed9ng:<\/strong> C\u00e1c h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u trong t\u01b0\u01a1ng lai c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng thu\u1eadt to\u00e1n h\u1ecdc m\u00e1y \u0111\u1ec3 t\u1ef1 \u0111\u1ed9ng x\u00e1c \u0111\u1ecbnh v\u00e0 t\u1ea1o c\u00e1c ch\u1ec9 m\u1ee5c gi\u00fap c\u1ea3i thi\u1ec7n hi\u1ec7u su\u1ea5t truy v\u1ea5n.<\/p>\n<\/li>\n

              3. \n

                T\u1ed1i \u01b0u h\u00f3a \u0111\u1ed9ng theo th\u1eddi gian th\u1ef1c:<\/strong> T\u1ed1i \u01b0u h\u00f3a \u0111\u1ed9ng c\u00f3 th\u1ec3 tr\u1edf n\u00ean ph\u1ee9c t\u1ea1p h\u01a1n, cho ph\u00e9p c\u00e1c k\u1ebf ho\u1ea1ch th\u1ef1c thi th\u00edch \u1ee9ng theo th\u1eddi gian th\u1ef1c d\u1ef1a tr\u00ean vi\u1ec7c thay \u0111\u1ed5i ph\u00e2n ph\u1ed1i d\u1eef li\u1ec7u v\u00e0 kh\u1ed1i l\u01b0\u1ee3ng c\u00f4ng vi\u1ec7c.<\/p>\n<\/li>\n

              4. \n

                K\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n d\u1ef1a tr\u00ean \u0111\u1ed3 th\u1ecb:<\/strong> C\u00f3 th\u1ec3 kh\u00e1m ph\u00e1 c\u00e1c bi\u1ec3u di\u1ec5n \u0111\u1ed3 th\u1ecb c\u1ee7a c\u00e1c k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n, cho ph\u00e9p t\u1ea1o ra c\u00e1c m\u1ed1i quan h\u1ec7 ph\u1ee9c t\u1ea1p h\u01a1n gi\u1eefa c\u00e1c ho\u1ea1t \u0111\u1ed9ng v\u00e0 chi\u1ebfn l\u01b0\u1ee3c t\u1ed1i \u01b0u h\u00f3a.<\/p>\n<\/li>\n<\/ol>\n

                C\u00e1ch s\u1eed d\u1ee5ng ho\u1eb7c li\u00ean k\u1ebft m\u00e1y ch\u1ee7 proxy v\u1edbi K\u1ebf ho\u1ea1ch th\u1ef1c thi (SQL)<\/h2>\n

                M\u00e1y ch\u1ee7 proxy c\u00f3 th\u1ec3 \u0111\u00f3ng vai tr\u00f2 t\u1ed1i \u01b0u h\u00f3a k\u1ebf ho\u1ea1ch th\u1ef1c thi trong SQL b\u1eb1ng c\u00e1ch \u0111\u00f3ng vai tr\u00f2 trung gian gi\u1eefa m\u00e1y kh\u00e1ch v\u00e0 m\u00e1y ch\u1ee7 c\u01a1 s\u1edf d\u1eef li\u1ec7u. H\u1ecd c\u00f3 th\u1ec3 gi\u00fap \u0111\u1ee1 theo nh\u1eefng c\u00e1ch sau:<\/p>\n

                  \n
                1. \n

                  B\u1ed9 nh\u1edb \u0111\u1ec7m:<\/strong> M\u00e1y ch\u1ee7 proxy c\u00f3 th\u1ec3 l\u01b0u tr\u1eef c\u00e1c truy v\u1ea5n \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n th\u01b0\u1eddng xuy\u00ean v\u00e0 k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n t\u01b0\u01a1ng \u1ee9ng c\u1ee7a ch\u00fang. \u0110i\u1ec1u n\u00e0y l\u00e0m gi\u1ea3m t\u1ea3i tr\u00ean m\u00e1y ch\u1ee7 c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 c\u1ea3i thi\u1ec7n th\u1eddi gian ph\u1ea3n h\u1ed3i cho c\u00e1c truy v\u1ea5n gi\u1ed1ng nhau ti\u1ebfp theo.<\/p>\n<\/li>\n

                2. \n

                  C\u00e2n b\u1eb1ng t\u1ea3i:<\/strong> Trong m\u00f4i tr\u01b0\u1eddng c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u00e2n t\u00e1n, m\u00e1y ch\u1ee7 proxy c\u00f3 th\u1ec3 c\u00e2n b\u1eb1ng t\u1ea3i truy v\u1ea5n tr\u00ean nhi\u1ec1u m\u00e1y ch\u1ee7 c\u01a1 s\u1edf d\u1eef li\u1ec7u d\u1ef1a tr\u00ean ph\u00e2n t\u00edch k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n c\u1ee7a ch\u00fang.<\/p>\n<\/li>\n

                3. \n

                  N\u00e9n v\u00e0 thu nh\u1ecf:<\/strong> M\u00e1y ch\u1ee7 proxy c\u00f3 th\u1ec3 n\u00e9n v\u00e0 thu nh\u1ecf c\u00e1c truy v\u1ea5n SQL tr\u01b0\u1edbc khi g\u1eedi ch\u00fang \u0111\u1ebfn m\u00e1y ch\u1ee7 c\u01a1 s\u1edf d\u1eef li\u1ec7u, gi\u1ea3m chi ph\u00ed m\u1ea1ng v\u00e0 c\u1ea3i thi\u1ec7n th\u1eddi gian th\u1ef1c hi\u1ec7n truy v\u1ea5n.<\/p>\n<\/li>\n

                4. \n

                  \u0110\u1ecbnh tuy\u1ebfn truy v\u1ea5n:<\/strong> M\u00e1y ch\u1ee7 proxy c\u00f3 th\u1ec3 \u0111\u1ecbnh tuy\u1ebfn truy v\u1ea5n \u0111\u1ebfn m\u00e1y ch\u1ee7 c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u00f9 h\u1ee3p nh\u1ea5t d\u1ef1a tr\u00ean ph\u00e2n t\u00edch k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n, \u0111\u1ea3m b\u1ea3o hi\u1ec7u su\u1ea5t truy v\u1ea5n t\u1ed1t h\u01a1n.<\/p>\n<\/li>\n<\/ol>\n

                  Li\u00ean k\u1ebft li\u00ean quan<\/h2>\n

                  \u0110\u1ec3 bi\u1ebft th\u00eam th\u00f4ng tin v\u1ec1 K\u1ebf ho\u1ea1ch th\u1ef1c thi (SQL) v\u00e0 t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n trong h\u1ec7 th\u1ed1ng c\u01a1 s\u1edf d\u1eef li\u1ec7u, b\u1ea1n c\u00f3 th\u1ec3 tham kh\u1ea3o c\u00e1c t\u00e0i nguy\u00ean sau:<\/p>\n

                    \n
                  1. Hi\u1ec3u k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n<\/a><\/li>\n
                  2. K\u1ebf ho\u1ea1ch th\u1ef1c thi m\u00e1y ch\u1ee7 SQL<\/a><\/li>\n
                  3. K\u1ef9 thu\u1eadt t\u1ed1i \u01b0u h\u00f3a c\u01a1 s\u1edf d\u1eef li\u1ec7u<\/a><\/li>\n<\/ol>\n

                    Hi\u1ec3u \u0111\u01b0\u1ee3c s\u1ef1 ph\u1ee9c t\u1ea1p c\u1ee7a c\u00e1c k\u1ebf ho\u1ea1ch th\u1ef1c thi trong SQL l\u00e0 r\u1ea5t quan tr\u1ecdng \u0111\u1ed1i v\u1edbi c\u00e1c nh\u00e0 ph\u00e1t tri\u1ec3n v\u00e0 qu\u1ea3n tr\u1ecb vi\u00ean \u0111ang t\u00ecm c\u00e1ch t\u1ed1i \u01b0u h\u00f3a hi\u1ec7u su\u1ea5t c\u01a1 s\u1edf d\u1eef li\u1ec7u c\u1ee7a h\u1ecd v\u00e0 n\u00e2ng cao tr\u1ea3i nghi\u1ec7m t\u1ed5ng th\u1ec3 c\u1ee7a ng\u01b0\u1eddi d\u00f9ng. B\u1eb1ng c\u00e1ch n\u1eafm b\u1eaft ho\u1ea1t \u0111\u1ed9ng n\u1ed9i b\u1ed9 c\u1ee7a k\u1ebf ho\u1ea1ch th\u1ef1c hi\u1ec7n, h\u1ecd c\u00f3 th\u1ec3 \u0111\u01b0a ra quy\u1ebft \u0111\u1ecbnh s\u00e1ng su\u1ed1t, tinh ch\u1ec9nh c\u00e1c truy v\u1ea5n v\u00e0 \u0111\u1ea3m b\u1ea3o truy xu\u1ea5t d\u1eef li\u1ec7u hi\u1ec7u qu\u1ea3, bi\u1ebfn n\u00f3 tr\u1edf th\u00e0nh m\u1ed9t kh\u00eda c\u1ea1nh kh\u00f4ng th\u1ec3 thi\u1ebfu c\u1ee7a h\u1ec7 th\u1ed1ng qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u hi\u1ec7n \u0111\u1ea1i.<\/p>","protected":false},"featured_media":0,"menu_order":0,"template":"","meta":{"_acf_changed":false,"content-type":"","inline_featured_image":false,"footnotes":""},"class_list":["post-477146","wiki","type-wiki","status-publish","hentry"],"acf":{"faq_title":"Frequently Asked Questions about Execution Plan (SQL) in Database Management Systems<\/mark>","faq_items":[{"question":"What is an Execution Plan in SQL?","answer":"

                    An execution plan in SQL is a detailed roadmap that the database management system (DBMS) follows to execute a specific SQL query efficiently. It outlines the steps and operations the DBMS will use to retrieve, join, filter, and process data to fulfill the query's requirements.<\/p>"},{"question":"How does an Execution Plan work?","answer":"

                    When a query is submitted to the DBMS, it undergoes a multi-step process before the actual data retrieval and processing can take place. The DBMS first parses the SQL query to ensure its correctness, then the query optimizer comes into play, exploring different execution plans and choosing the most efficient one. The selected plan is then generated and executed, with the DBMS employing various techniques like index scans, joins, and sorting to fetch and process data.<\/p>"},{"question":"What are the key features of an Execution Plan in SQL?","answer":"

                    The key features of an execution plan in SQL include optimization, flexibility, dynamic optimization, and statistics-based decision-making. The optimizer evaluates various execution plans and assigns a cost to each, choosing the plan with the lowest cost for execution.<\/p>"},{"question":"What types of Execution Plans exist?","answer":"

                    Several types of execution plans can be considered by the query optimizer, such as table scan plan, index scan plan, nested loop join plan, hash join plan, merge join plan, and sort plan. The choice of plan depends on factors like query complexity, data distribution, and available resources.<\/p>"},{"question":"How can I use Execution Plans in SQL?","answer":"

                    You can use execution plans in SQL for query optimization, performance troubleshooting, and index design. By understanding the execution plan, you can identify inefficient queries, optimize their structure, and improve overall database performance.<\/p>"},{"question":"What problems can be encountered with Execution Plans, and how can they be solved?","answer":"

                    Common problems with execution plans include missing or stale statistics, inefficient join strategies, and improper index selection. To address these issues, regularly update statistics, use query hints, and consider manual index specification.<\/p>"},{"question":"What are the future perspectives related to Execution Plans in SQL?","answer":"

                    The future of execution plans in SQL is expected to involve machine learning-based optimization, automated indexing, real-time dynamic optimization, and potentially, graph-based representations of execution plans.<\/p>"},{"question":"How can proxy servers be associated with Execution Plans in SQL?","answer":"

                    Proxy servers can optimize the execution plan in SQL by caching queries, load balancing, compressing and minifying queries, and routing queries to the most appropriate database server based on execution plan analysis. This enhances overall query performance and database management efficiency.<\/p>"}]},"_links":{"self":[{"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/wiki\/477146","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\/477146\/revisions"}],"wp:attachment":[{"href":"https:\/\/oneproxy.pro\/vn\/wp-json\/wp\/v2\/media?parent=477146"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}