{"id":9430,"date":"2025-04-17T13:43:15","date_gmt":"2025-04-17T06:43:15","guid":{"rendered":"https:\/\/mb668s.com\/cam-nang-7mb66-xoc-dia\/?p=9430"},"modified":"2026-03-27T17:21:03","modified_gmt":"2026-03-27T10:21:03","slug":"inner-join-trong-sql","status":"publish","type":"post","link":"https:\/\/mb668s.com\/cam-nang-7mb66-xoc-dia\/tu-van-nghe-nghiep\/inner-join-trong-sql","title":{"rendered":"INNER JOIN trong SQL l\u00e0 g\u00ec? C\u00e1ch ho\u1ea1t \u0111\u1ed9ng v\u00e0 c\u00fa ph\u00e1p chi ti\u1ebft"},"content":{"rendered":"\n

L\u00e0m vi\u1ec7c v\u1edbi c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 kh\u00f4ng ch\u1ec9 y\u00eau c\u1ea7u hi\u1ec3u v\u1ec1 c\u1ea5u tr\u00fac b\u1ea3ng m\u00e0 c\u00f2n \u0111\u00f2i h\u1ecfi kh\u1ea3 n\u0103ng k\u1ebft n\u1ed1i th\u00f4ng tin m\u1ed9t c\u00e1ch logic v\u00e0 hi\u1ec7u qu\u1ea3. Kh\u00e1i ni\u1ec7m INNER JOIN trong SQL<\/strong> th\u01b0\u1eddng xuy\u00ean xu\u1ea5t hi\u1ec7n nh\u01b0 m\u1ed9t ph\u01b0\u01a1ng ph\u00e1p ph\u1ed5 bi\u1ebfn \u0111\u1ec3 truy xu\u1ea5t d\u1eef li\u1ec7u li\u00ean b\u1ea3ng, ph\u1ee5c v\u1ee5 cho c\u00e1c t\u00ecnh hu\u1ed1ng th\u1ef1c t\u1ebf t\u1eeb ph\u00e2n t\u00edch b\u00e1o c\u00e1o \u0111\u1ebfn ph\u00e1t tri\u1ec3n \u1ee9ng d\u1ee5ng. Vi\u1ec7c s\u1eed d\u1ee5ng \u0111\u00fang v\u00e0 t\u1ed1i \u01b0u ph\u00e9p JOIN n\u00e0y l\u00e0 n\u1ec1n t\u1ea3ng quan tr\u1ecdng gi\u00fap b\u1ea1n l\u00e0m ch\u1ee7 k\u1ef9 n\u0103ng truy v\u1ea5n d\u1eef li\u1ec7u trong m\u00f4i tr\u01b0\u1eddng chuy\u00ean nghi\u1ec7p.<\/p>\n\n\n\n

\"INNER<\/figure>\n\n\n\n

INNER JOIN trong SQL l\u00e0 g\u00ec?<\/h2>\n\n\n\n
\n

INNER JOIN trong SQL l\u00e0 m\u1ed9t ph\u00e9p n\u1ed1i (JOIN) d\u00f9ng \u0111\u1ec3 k\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb hai ho\u1eb7c nhi\u1ec1u b\u1ea3ng d\u1ef1a tr\u00ean gi\u00e1 tr\u1ecb chung \u1edf c\u1ed9t li\u00ean quan.<\/strong><\/p>\n<\/blockquote>\n\n\n\n

Ph\u00e9p n\u1ed1i n\u00e0y ch\u1ec9 tr\u1ea3 v\u1ec1 nh\u1eefng b\u1ea3n ghi c\u00f3 gi\u00e1 tr\u1ecb kh\u1edbp \u1edf c\u1ea3 hai b\u1ea3ng<\/strong>, \u0111\u1ed3ng th\u1eddi lo\u1ea1i b\u1ecf c\u00e1c d\u00f2ng kh\u00f4ng li\u00ean k\u1ebft. INNER JOIN l\u00e0 lo\u1ea1i Join ph\u1ed5 bi\u1ebfn nh\u1ea5t trong SQL v\u00e0 th\u01b0\u1eddng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng khi c\u1ea7n l\u1ea5y d\u1eef li\u1ec7u c\u00f3 li\u00ean h\u1ec7 logic ch\u1eb7t ch\u1ebd<\/strong> gi\u1eefa c\u00e1c b\u1ea3ng, ch\u1eb3ng h\u1ea1n nh\u01b0 \u0111\u01a1n h\u00e0ng k\u00e8m th\u00f4ng tin kh\u00e1ch h\u00e0ng, s\u1ea3n ph\u1ea9m k\u00e8m danh m\u1ee5c,…<\/p>\n\n\n\n

C\u00e1ch ho\u1ea1t \u0111\u1ed9ng v\u00e0 vai tr\u00f2 th\u1ef1c t\u1ebf c\u1ee7a INNER JOIN<\/h2>\n\n\n\n

INNER JOIN l\u1ecdc d\u1eef li\u1ec7u t\u1eeb nhi\u1ec1u b\u1ea3ng d\u1ef1a tr\u00ean \u0111i\u1ec1u ki\u1ec7n kh\u1edbp nhau, gi\u00fap truy v\u1ea5n t\u1eadp trung, ch\u00ednh x\u00e1c v\u00e0 c\u00f3 \u00fd ngh\u0129a trong m\u1ed1i quan h\u1ec7 gi\u1eefa c\u00e1c b\u1ea3ng.<\/p>\n\n\n\n

Nguy\u00ean l\u00fd l\u1ecdc d\u1eef li\u1ec7u gi\u1eefa c\u00e1c b\u1ea3ng<\/h3>\n\n\n\n

INNER JOIN ho\u1ea1t \u0111\u1ed9ng d\u1ef1a tr\u00ean nguy\u00ean l\u00fd \u0111\u1ed1i chi\u1ebfu gi\u00e1 tr\u1ecb gi\u1eefa c\u00e1c c\u1ed9t c\u00f3 li\u00ean quan trong hai b\u1ea3ng d\u1eef li\u1ec7u. Khi th\u1ef1c hi\u1ec7n INNER JOIN, h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u s\u1ebd ki\u1ec3m tra t\u1eebng d\u00f2ng trong b\u1ea3ng th\u1ee9 nh\u1ea5t v\u1edbi t\u1eebng d\u00f2ng trong b\u1ea3ng th\u1ee9 hai \u0111\u1ec3 t\u00ecm ra nh\u1eefng c\u1eb7p b\u1ea3n ghi c\u00f3 gi\u00e1 tr\u1ecb t\u01b0\u01a1ng \u1ee9ng t\u1ea1i c\u1ed9t \u0111\u01b0\u1ee3c ch\u1ec9 \u0111\u1ecbnh trong m\u1ec7nh \u0111\u1ec1 ON. N\u1ebfu \u0111i\u1ec1u ki\u1ec7n n\u00e0y \u0111\u00fang, b\u1ea3n ghi k\u1ebft qu\u1ea3 s\u1ebd \u0111\u01b0\u1ee3c th\u00eam v\u00e0o t\u1eadp truy v\u1ea5n \u0111\u1ea7u ra. N\u1ebfu kh\u00f4ng, c\u1ea3 hai b\u1ea3n ghi s\u1ebd b\u1ecb lo\u1ea1i b\u1ecf kh\u1ecfi k\u1ebft qu\u1ea3.<\/p>\n\n\n\n

T\u1ea7m quan tr\u1ecdng c\u1ee7a INNER JOIN trong truy v\u1ea5n quan h\u1ec7<\/h3>\n\n\n\n

Trong c\u00e1c h\u1ec7 th\u1ed1ng d\u1eef li\u1ec7u l\u1edbn, n\u01a1i th\u00f4ng tin \u0111\u01b0\u1ee3c ph\u00e2n t\u00e1ch v\u00e0 l\u01b0u tr\u1eef \u1edf nhi\u1ec1u b\u1ea3ng kh\u00e1c nhau \u0111\u1ec3 t\u1ed1i \u01b0u h\u00f3a hi\u1ec7u su\u1ea5t v\u00e0 tr\u00e1nh tr\u00f9ng l\u1eb7p, vi\u1ec7c truy xu\u1ea5t d\u1eef li\u1ec7u \u0111\u1ed3ng b\u1ed9 v\u00e0 logic l\u00e0 \u0111i\u1ec1u t\u1ed1i quan tr\u1ecdng. INNER JOIN cho ph\u00e9p k\u1ebft h\u1ee3p d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch c\u00f3 ki\u1ec3m so\u00e1t, ch\u1ec9 tr\u1ea3 v\u1ec1 c\u00e1c gi\u00e1 tr\u1ecb th\u1ef1c s\u1ef1 li\u00ean k\u1ebft v\u1edbi nhau gi\u1eefa c\u00e1c b\u1ea3ng. \u0110i\u1ec1u n\u00e0y gi\u00fap \u0111\u1ea3m b\u1ea3o t\u00ednh nh\u1ea5t qu\u00e1n, ch\u00ednh x\u00e1c v\u00e0 tr\u00e1nh r\u1ed1i lo\u1ea1n khi t\u1ed5ng h\u1ee3p b\u00e1o c\u00e1o, ph\u00e2n t\u00edch d\u1eef li\u1ec7u ho\u1eb7c x\u00e2y d\u1ef1ng API.<\/p>\n\n\n\n

Khi n\u00e0o n\u00ean s\u1eed d\u1ee5ng INNER JOIN trong th\u1ef1c t\u1ebf?<\/h3>\n\n\n\n

INNER JOIN n\u00ean \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng khi b\u1ea1n ch\u1ec9 quan t\u00e2m \u0111\u1ebfn c\u00e1c b\u1ea3n ghi c\u00f3 m\u1ed1i li\u00ean k\u1ebft r\u00f5 r\u00e0ng gi\u1eefa c\u00e1c b\u1ea3ng. V\u00ed d\u1ee5, khi c\u1ea7n li\u1ec7t k\u00ea c\u00e1c \u0111\u01a1n h\u00e0ng \u0111\u00e3 \u0111\u01b0\u1ee3c \u0111\u1eb7t th\u00e0nh c\u00f4ng c\u00f9ng v\u1edbi th\u00f4ng tin kh\u00e1ch h\u00e0ng t\u01b0\u01a1ng \u1ee9ng, b\u1ea1n s\u1ebd ch\u1ec9 mu\u1ed1n l\u1ea5y c\u00e1c \u0111\u01a1n h\u00e0ng \u0111\u00e3 g\u1eafn v\u1edbi m\u00e3 kh\u00e1ch h\u00e0ng h\u1ee3p l\u1ec7 \u2013 t\u1ee9c l\u00e0 t\u1ed3n t\u1ea1i \u1edf c\u1ea3 b\u1ea3ng orders v\u00e0 b\u1ea3ng customers. Trong c\u00e1c t\u00ecnh hu\u1ed1ng n\u00e0y, INNER JOIN s\u1ebd lo\u1ea1i b\u1ecf c\u00e1c b\u1ea3n ghi r\u00e1c ho\u1eb7c thi\u1ebfu li\u00ean k\u1ebft, gi\u00fap k\u1ebft qu\u1ea3 truy v\u1ea5n ch\u00ednh x\u00e1c v\u00e0 s\u1ea1ch d\u1eef li\u1ec7u h\u01a1n.<\/p>\n\n\n\n

M\u00f4 t\u1ea3 tr\u1ef1c quan b\u1eb1ng s\u01a1 \u0111\u1ed3, b\u1ea3ng v\u00ed d\u1ee5<\/h3>\n\n\n\n

Gi\u1ea3 s\u1eed b\u1ea1n c\u00f3 hai b\u1ea3ng sau:<\/p>\n\n\n\n

B\u1ea3ng customers: g\u1ed3m c\u00e1c c\u1ed9t customer_id, name<\/p>\n\n\n\n

B\u1ea3ng orders: g\u1ed3m c\u00e1c c\u1ed9t order_id, customer_id, total<\/p>\n\n\n\n

Khi d\u00f9ng INNER JOIN \u0111\u1ec3 l\u1ea5y danh s\u00e1ch \u0111\u01a1n h\u00e0ng k\u00e8m t\u00ean kh\u00e1ch h\u00e0ng:<\/p>\n\n\n\n

sql<\/p>\n\n\n\n

SELECT customers.name, orders.order_id, orders.total<\/p>\n\n\n\n

FROM customers<\/p>\n\n\n\n

INNER JOIN orders ON customers.customer_id = orders.customer_id;<\/p>\n\n\n\n

K\u1ebft qu\u1ea3 truy v\u1ea5n ch\u1ec9 bao g\u1ed3m c\u00e1c d\u00f2ng m\u00e0 customer_id t\u1ed3n t\u1ea1i \u1edf c\u1ea3 hai b\u1ea3ng \u2013 ngh\u0129a l\u00e0 ch\u1ec9 nh\u1eefng \u0111\u01a1n h\u00e0ng c\u00f3 kh\u00e1ch h\u00e0ng h\u1ee3p l\u1ec7.<\/p>\n\n\n\n

C\u00fa ph\u00e1p INNER JOIN trong SQL<\/h2>\n\n\n\n

C\u00fa ph\u00e1p INNER JOIN \u0111\u01a1n gi\u1ea3n, d\u1ec5 \u0111\u1ecdc v\u00e0 linh ho\u1ea1t, cho ph\u00e9p k\u1ebft h\u1ee3p c\u00e1c b\u1ea3ng th\u00f4ng qua \u0111i\u1ec1u ki\u1ec7n trong m\u1ec7nh \u0111\u1ec1 ON<\/code>, h\u1ed7 tr\u1ee3 truy v\u1ea5n d\u1eef li\u1ec7u li\u00ean b\u1ea3ng hi\u1ec7u qu\u1ea3.<\/p>\n\n\n\n

C\u00fa ph\u00e1p chu\u1ea9n v\u1edbi INNER JOIN … ON<\/h3>\n\n\n\n

C\u00e2u l\u1ec7nh INNER JOIN th\u01b0\u1eddng \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng theo c\u00fa ph\u00e1p c\u01a1 b\u1ea3n sau:<\/p>\n\n\n\n

sql<\/p>\n\n\n\n

SELECT t\u00ean_c\u1ed9t<\/p>\n\n\n\n

FROM b\u1ea3ng_1<\/p>\n\n\n\n

INNER JOIN b\u1ea3ng_2<\/p>\n\n\n\n

ON b\u1ea3ng_1.t\u00ean_c\u1ed9t = b\u1ea3ng_2.t\u00ean_c\u1ed9t;<\/p>\n\n\n\n

Trong \u0111\u00f3:<\/p>\n\n\n\n

SELECT d\u00f9ng \u0111\u1ec3 ch\u1ec9 \u0111\u1ecbnh c\u00e1c c\u1ed9t c\u1ea7n truy xu\u1ea5t t\u1eeb hai b\u1ea3ng.<\/p>\n\n\n\n

INNER JOIN l\u00e0 t\u1eeb kh\u00f3a th\u1ef1c hi\u1ec7n ph\u00e9p n\u1ed1i n\u1ed9i b\u1ed9 gi\u1eefa hai b\u1ea3ng.<\/p>\n\n\n\n

ON \u0111\u1ecbnh ngh\u0129a \u0111i\u1ec1u ki\u1ec7n n\u1ed1i, th\u01b0\u1eddng d\u1ef1a tr\u00ean c\u00e1c kh\u00f3a li\u00ean k\u1ebft gi\u1eefa hai b\u1ea3ng (v\u00ed d\u1ee5: kh\u00f3a ch\u00ednh v\u00e0 kh\u00f3a ngo\u1ea1i).<\/p>\n\n\n\n

C\u00fa ph\u00e1p n\u00e0y gi\u00fap truy xu\u1ea5t c\u00e1c b\u1ea3n ghi ch\u1ec9 khi \u0111i\u1ec1u ki\u1ec7n n\u1ed1i \u0111\u01b0\u1ee3c th\u1ecfa m\u00e3n, v\u00e0 l\u00e0 c\u00e1ch vi\u1ebft ph\u1ed5 bi\u1ebfn, d\u1ec5 \u0111\u1ecdc, d\u1ec5 b\u1ea3o tr\u00ec trong c\u00e1c h\u1ec7 th\u1ed1ng SQL l\u1edbn.<\/p>\n\n\n\n

V\u00ed d\u1ee5 minh h\u1ecda:<\/p>\n\n\n\n

sql<\/p>\n\n\n\n

SELECT employees.name, departments.department_name<\/p>\n\n\n\n

FROM employees<\/p>\n\n\n\n

INNER JOIN departments<\/p>\n\n\n\n

ON employees.department_id = departments.department_id;<\/p>\n\n\n\n

C\u00e2u l\u1ec7nh tr\u00ean gi\u00fap l\u1ea5y t\u00ean nh\u00e2n vi\u00ean c\u00f9ng t\u00ean ph\u00f2ng ban t\u01b0\u01a1ng \u1ee9ng, ch\u1ec9 trong tr\u01b0\u1eddng h\u1ee3p c\u1ea3 hai b\u1ea3ng c\u00f3 d\u1eef li\u1ec7u li\u00ean k\u1ebft h\u1ee3p l\u1ec7.<\/p>\n\n\n\n

Gi\u1ea3i th\u00edch t\u1eebng th\u00e0nh ph\u1ea7n trong c\u00e2u l\u1ec7nh<\/h3>\n\n\n\n

SELECT: X\u00e1c \u0111\u1ecbnh c\u00e1c c\u1ed9t s\u1ebd hi\u1ec3n th\u1ecb trong k\u1ebft qu\u1ea3, c\u00f3 th\u1ec3 \u0111\u1ebfn t\u1eeb m\u1ed9t ho\u1eb7c c\u1ea3 hai b\u1ea3ng.<\/p>\n\n\n\n

FROM b\u1ea3ng_1: X\u00e1c \u0111\u1ecbnh b\u1ea3ng ch\u00ednh m\u00e0 truy v\u1ea5n b\u1eaft \u0111\u1ea7u.<\/p>\n\n\n\n

INNER JOIN b\u1ea3ng_2: Th\u1ef1c hi\u1ec7n ph\u00e9p n\u1ed1i v\u1edbi b\u1ea3ng th\u1ee9 hai.<\/p>\n\n\n\n

ON b\u1ea3ng_1.c\u1ed9t = b\u1ea3ng_2.c\u1ed9t: \u0110i\u1ec1u ki\u1ec7n n\u1ed1i \u2013 th\u01b0\u1eddng l\u00e0 hai c\u1ed9t c\u00f3 gi\u00e1 tr\u1ecb logic t\u01b0\u01a1ng \u0111\u01b0\u01a1ng (vd: ID).<\/p>\n\n\n\n

Vi\u1ec7c t\u00e1ch r\u00f5 c\u00e1c th\u00e0nh ph\u1ea7n n\u00e0y gi\u00fap truy v\u1ea5n c\u00f3 t\u00ednh m\u00f4-\u0111un, d\u1ec5 m\u1edf r\u1ed9ng khi c\u1ea7n JOIN th\u00eam nhi\u1ec1u b\u1ea3ng ho\u1eb7c th\u00eam \u0111i\u1ec1u ki\u1ec7n l\u1ecdc chi ti\u1ebft b\u1eb1ng WHERE, GROUP BY hay ORDER BY.<\/p>\n\n\n\n

\n

Xem th\u00eam: Tuy\u1ec3n D\u1ee5ng IT ph\u1ea7n m\u1ec1m<\/a> ta\u0323i Careerlink.vn<\/p>\n<\/blockquote>\n\n\n\n

\u1ee8ng d\u1ee5ng n\u00e2ng cao c\u1ee7a INNER JOIN<\/h2>\n\n\n\n

INNER JOIN c\u00f3 th\u1ec3 d\u00f9ng k\u1ebft h\u1ee3p nhi\u1ec1u b\u1ea3ng, k\u00e8m theo c\u00e1c \u0111i\u1ec1u ki\u1ec7n logic v\u00e0 m\u1ec7nh \u0111\u1ec1 nh\u01b0 GROUP BY, ORDER BY \u0111\u1ec3 x\u00e2y d\u1ef1ng truy v\u1ea5n ph\u1ee9c t\u1ea1p, \u0111a t\u1ea7ng.<\/p>\n\n\n\n

V\u00ed d\u1ee5 k\u1ebft h\u1ee3p hai b\u1ea3ng \u0111\u01a1n gi\u1ea3n<\/h3>\n\n\n\n

M\u1ed9t trong nh\u1eefng \u1ee9ng d\u1ee5ng ph\u1ed5 bi\u1ebfn nh\u1ea5t c\u1ee7a INNER JOIN l\u00e0 k\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb hai b\u1ea3ng c\u00f3 quan h\u1ec7 kh\u00f3a ngo\u1ea1i \u2013 kh\u00f3a ch\u00ednh. V\u00ed d\u1ee5, b\u1ea1n c\u00f3 b\u1ea3ng students v\u00e0 b\u1ea3ng classes, m\u1ed7i h\u1ecdc sinh s\u1ebd c\u00f3 m\u1ed9t class_id li\u00ean k\u1ebft \u0111\u1ebfn b\u1ea3ng l\u1edbp h\u1ecdc. Khi b\u1ea1n c\u1ea7n l\u1ea5y t\u00ean h\u1ecdc sinh v\u00e0 t\u00ean l\u1edbp t\u01b0\u01a1ng \u1ee9ng:<\/p>\n\n\n\n

sql<\/p>\n\n\n\n

SELECT students.name, classes.class_name<\/p>\n\n\n\n

FROM students<\/p>\n\n\n\n

INNER JOIN classes<\/p>\n\n\n\n

ON students.class_id = classes.class_id;<\/p>\n\n\n\n

C\u00e2u l\u1ec7nh n\u00e0y tr\u1ea3 v\u1ec1 danh s\u00e1ch h\u1ecdc sinh ch\u1ec9 khi c\u00f3 th\u00f4ng tin l\u1edbp h\u1ecdc t\u01b0\u01a1ng \u1ee9ng, lo\u1ea1i b\u1ecf nh\u1eefng b\u1ea3n ghi kh\u00f4ng li\u00ean k\u1ebft h\u1ee3p l\u1ec7.<\/p>\n\n\n\n

Gi\u1ea3i th\u00edch chi ti\u1ebft k\u1ebft qu\u1ea3 truy v\u1ea5n<\/h3>\n\n\n\n

INNER JOIN ch\u1ec9 tr\u1ea3 v\u1ec1 c\u00e1c d\u00f2ng c\u00f3 gi\u00e1 tr\u1ecb kh\u1edbp t\u1ea1i \u0111i\u1ec1u ki\u1ec7n n\u1ed1i. \u0110i\u1ec1u n\u00e0y c\u00f3 ngh\u0129a l\u00e0 n\u1ebfu m\u1ed9t h\u1ecdc sinh ch\u01b0a \u0111\u01b0\u1ee3c g\u00e1n l\u1edbp (class_id kh\u00f4ng c\u00f3 trong b\u1ea3ng classes), b\u1ea3n ghi \u0111\u00f3 s\u1ebd kh\u00f4ng xu\u1ea5t hi\u1ec7n trong k\u1ebft qu\u1ea3 truy v\u1ea5n. C\u01a1 ch\u1ebf l\u1ecdc n\u00e0y gi\u00fap gi\u1eef cho d\u1eef li\u1ec7u \u0111\u1ea7u ra \u201cs\u1ea1ch\u201d v\u00e0 ch\u1ec9 bao g\u1ed3m nh\u1eefng th\u00f4ng tin li\u00ean quan th\u1ef1c s\u1ef1.<\/p>\n\n\n\n

INNER JOIN v\u1edbi nhi\u1ec1u b\u1ea3ng (multi-table JOIN)<\/h3>\n\n\n\n

SQL h\u1ed7 tr\u1ee3 vi\u1ec7c n\u1ed1i nhi\u1ec1u b\u1ea3ng trong c\u00f9ng m\u1ed9t truy v\u1ea5n th\u00f4ng qua chu\u1ed7i c\u00e1c INNER JOIN. V\u00ed d\u1ee5: l\u1ea5y th\u00f4ng tin \u0111\u01a1n h\u00e0ng, kh\u00e1ch h\u00e0ng v\u00e0 s\u1ea3n ph\u1ea9m:<\/p>\n\n\n\n

sql<\/p>\n\n\n\n

SELECT orders.order_id, customers.name, products.product_name<\/p>\n\n\n\n

FROM orders<\/p>\n\n\n\n

INNER JOIN customers ON orders.customer_id = customers.customer_id<\/p>\n\n\n\n

INNER JOIN products ON orders.product_id = products.product_id;<\/p>\n\n\n\n

C\u00e2u truy v\u1ea5n n\u00e0y ch\u1ec9 tr\u1ea3 v\u1ec1 c\u00e1c \u0111\u01a1n h\u00e0ng h\u1ee3p l\u1ec7, c\u00f3 kh\u00e1ch h\u00e0ng v\u00e0 s\u1ea3n ph\u1ea9m t\u01b0\u01a1ng \u1ee9ng. Vi\u1ec7c JOIN nhi\u1ec1u b\u1ea3ng cho ph\u00e9p b\u1ea1n t\u1ed5ng h\u1ee3p d\u1eef li\u1ec7u t\u1eeb c\u00e1c ngu\u1ed3n li\u00ean quan m\u1ed9t c\u00e1ch m\u1ea1nh m\u1ebd v\u00e0 linh ho\u1ea1t.<\/p>\n\n\n\n

INNER JOIN v\u1edbi \u0111i\u1ec1u ki\u1ec7n AND, OR<\/h3>\n\n\n\n

Trong m\u1ed9t s\u1ed1 t\u00ecnh hu\u1ed1ng, b\u1ea1n c\u1ea7n \u00e1p d\u1ee5ng nhi\u1ec1u \u0111i\u1ec1u ki\u1ec7n \u0111\u1ec3 x\u00e1c \u0111\u1ecbnh s\u1ef1 li\u00ean k\u1ebft gi\u1eefa c\u00e1c b\u1ea3ng. INNER JOIN c\u00f3 th\u1ec3 k\u1ebft h\u1ee3p v\u1edbi to\u00e1n t\u1eed AND, OR trong ph\u1ea7n ON ho\u1eb7c WHERE:<\/p>\n\n\n\n

sql<\/p>\n\n\n\n

SELECT employees.name, departments.name<\/p>\n\n\n\n

FROM employees<\/p>\n\n\n\n

INNER JOIN departments<\/p>\n\n\n\n

ON employees.department_id = departments.id AND employees.active = 1;<\/p>\n\n\n\n

C\u00e2u truy v\u1ea5n n\u00e0y ch\u1ec9 l\u1ea5y nh\u1eefng nh\u00e2n vi\u00ean \u0111ang ho\u1ea1t \u0111\u1ed9ng (active = 1) v\u00e0 c\u00f3 ph\u00f2ng ban h\u1ee3p l\u1ec7. Vi\u1ec7c th\u00eam \u0111i\u1ec1u ki\u1ec7n logic gi\u00fap b\u1ea1n linh ho\u1ea1t ki\u1ec3m so\u00e1t k\u1ebft qu\u1ea3 \u0111\u1ea7u ra.<\/p>\n\n\n\n

K\u1ebft h\u1ee3p INNER JOIN v\u1edbi GROUP BY, ORDER BY<\/h3>\n\n\n\n

INNER JOIN th\u01b0\u1eddng \u0111\u01b0\u1ee3c k\u1ebft h\u1ee3p v\u1edbi c\u00e1c m\u1ec7nh \u0111\u1ec1 nh\u01b0 GROUP BY v\u00e0 ORDER BY \u0111\u1ec3 x\u1eed l\u00fd d\u1eef li\u1ec7u sau khi JOIN:<\/p>\n\n\n\n

sql<\/p>\n\n\n\n

SELECT departments.name, COUNT(employees.id) AS total_employees<\/p>\n\n\n\n

FROM departments<\/p>\n\n\n\n

INNER JOIN employees ON departments.id = employees.department_id<\/p>\n\n\n\n

GROUP BY departments.name<\/p>\n\n\n\n

ORDER BY total_employees DESC;<\/p>\n\n\n\n

C\u00e2u truy v\u1ea5n n\u00e0y th\u1ed1ng k\u00ea s\u1ed1 l\u01b0\u1ee3ng nh\u00e2n vi\u00ean theo t\u1eebng ph\u00f2ng ban, s\u1eafp x\u1ebfp gi\u1ea3m d\u1ea7n theo s\u1ed1 l\u01b0\u1ee3ng. Vi\u1ec7c k\u1ebft h\u1ee3p INNER JOIN v\u1edbi c\u00e1c m\u1ec7nh \u0111\u1ec1 t\u1ed5ng h\u1ee3p gi\u00fap truy v\u1ea5n c\u00f3 chi\u1ec1u s\u00e2u v\u00e0 ph\u00f9 h\u1ee3p cho c\u00e1c b\u00e1o c\u00e1o ph\u1ee9c t\u1ea1p.<\/p>\n\n\n\n

S\u1ef1 kh\u00e1c bi\u1ec7t khi d\u00f9ng INNER JOIN tr\u00ean MySQL, PostgreSQL, SQL Server, Oracle<\/strong><\/h3>\n\n\n\n

INNER JOIN l\u00e0 m\u1ed9t ph\u1ea7n trong chu\u1ea9n SQL v\u00e0 \u0111\u01b0\u1ee3c h\u1ed7 tr\u1ee3 tr\u00ean h\u1ea7u h\u1ebft c\u00e1c h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u (RDBMS) hi\u1ec7n nay nh\u01b0 MySQL, PostgreSQL, SQL Server v\u00e0 Oracle. Tuy nhi\u00ean, khi tri\u1ec3n khai trong th\u1ef1c t\u1ebf, s\u1ebd c\u00f3 m\u1ed9t s\u1ed1 kh\u00e1c bi\u1ec7t nh\u1ecf v\u1ec1 c\u00fa ph\u00e1p, c\u00e1ch x\u1eed l\u00fd NULL, hi\u1ec7u su\u1ea5t ho\u1eb7c c\u00e1c t\u00ednh n\u0103ng m\u1edf r\u1ed9ng<\/strong>.<\/p>\n\n\n\n

MySQL<\/strong><\/p>\n\n\n\n

H\u1ed7 tr\u1ee3 c\u00fa ph\u00e1p chu\u1ea9n c\u1ee7a INNER JOIN.<\/p>\n\n\n\n

Cho ph\u00e9p s\u1eed d\u1ee5ng USING()<\/code> thay cho ON<\/code> n\u1ebfu c\u1ed9t li\u00ean k\u1ebft tr\u00f9ng t\u00ean.<\/p>\n\n\n\n

H\u1ec7 th\u1ed1ng t\u1ed1i \u01b0u h\u00f3a t\u01b0\u01a1ng \u0111\u1ed1i nhanh, \u0111\u1eb7c bi\u1ec7t khi c\u00f3 ch\u1ec9 m\u1ee5c ph\u00f9 h\u1ee3p.<\/p>\n\n\n\n

sql<\/p>\n\n\n\n

SELECT <\/code>*<\/code><\/p>\n\n\n\n

FROM orders<\/code><\/p>\n\n\n\n

INNER JOIN<\/strong> customers <\/strong><\/code>USING<\/strong> (customer_id);<\/strong><\/code><\/p>\n\n\n\n

PostgreSQL<\/strong><\/p>\n\n\n\n

Tu\u00e2n th\u1ee7 ch\u1eb7t chu\u1ea9n SQL, c\u00fa ph\u00e1p INNER JOIN gi\u1ed1ng MySQL.<\/p>\n\n\n\n

H\u1ed7 tr\u1ee3 JOIN l\u1ed3ng nhau v\u00e0 subquery m\u1ea1nh m\u1ebd.<\/p>\n\n\n\n

C\u00f3 kh\u1ea3 n\u0103ng x\u1eed l\u00fd c\u00e1c \u0111i\u1ec1u ki\u1ec7n JOIN ph\u1ee9c t\u1ea1p h\u01a1n, k\u1ec3 c\u1ea3 bi\u1ec3u th\u1ee9c.<\/p>\n\n\n\n

sql<\/p>\n\n\n\n

SELECT <\/code>*<\/code><\/p>\n\n\n\n

FROM employees<\/code><\/p>\n\n\n\n

INNER JOIN departments<\/code><\/p>\n\n\n\n

ON employees.department_id <\/code>= departments.id;<\/code><\/p>\n\n\n\n

SQL Server<\/strong><\/p>\n\n\n\n

C\u00fa ph\u00e1p gi\u1ed1ng chu\u1ea9n, nh\u01b0ng c\u00f3 th\u1ec3 vi\u1ebft INNER JOIN<\/code> b\u1eb1ng JOIN<\/code> m\u00e0 kh\u00f4ng c\u1ea7n t\u1eeb kh\u00f3a INNER<\/code>.<\/p>\n\n\n\n

Cho ph\u00e9p k\u1ebft h\u1ee3p INNER JOIN v\u1edbi TOP<\/code>, WITH (NOLOCK)<\/code>, ho\u1eb7c c\u00e1c t\u00f9y ch\u1ecdn truy v\u1ea5n n\u00e2ng cao.<\/p>\n\n\n\n

Th\u01b0\u1eddng s\u1eed d\u1ee5ng t\u1eeb kh\u00f3a AS<\/code> r\u00f5 r\u00e0ng h\u01a1n \u0111\u1ec3 \u0111\u1eb7t b\u00ed danh b\u1ea3ng.<\/p>\n\n\n\n

sql<\/p>\n\n\n\n

SELECT e.name, d.name<\/code><\/p>\n\n\n\n

FROM employees <\/code>AS e<\/code><\/p>\n\n\n\n

JOIN departments <\/code>AS d<\/code><\/p>\n\n\n\n

ON e.department_id <\/code>= d.id;<\/code><\/p>\n\n\n\n

Oracle<\/strong><\/p>\n\n\n\n

C\u00fa ph\u00e1p INNER JOIN chu\u1ea9n \u0111\u01b0\u1ee3c h\u1ed7 tr\u1ee3 t\u1eeb Oracle 9i tr\u1edf l\u00ean.<\/p>\n\n\n\n

Oracle c\u0169 c\u00f3 th\u1ec3 d\u00f9ng c\u00fa ph\u00e1p c\u0169 v\u1edbi d\u1ea5u (*)<\/code>, nh\u01b0ng n\u00ean tr\u00e1nh.<\/p>\n\n\n\n

Oracle h\u1ed7 tr\u1ee3 hi\u1ec7u qu\u1ea3 khi JOIN k\u1ebft h\u1ee3p v\u1edbi c\u00e1c h\u00e0m ph\u00e2n t\u00edch ho\u1eb7c CTE (Common Table Expressions).<\/p>\n\n\n\n

sql<\/p>\n\n\n\n

SELECT <\/code>*<\/code><\/p>\n\n\n\n

FROM employees<\/code><\/p>\n\n\n\n

INNER JOIN departments<\/code><\/p>\n\n\n\n

ON employees.department_id <\/code>= departments.department_id;<\/code><\/p>\n\n\n\n

T\u1ed5ng k\u1ebft:<\/strong> <\/strong>D\u00f9 INNER JOIN v\u1ec1 c\u01a1 b\u1ea3n c\u00f3 c\u00fa ph\u00e1p th\u1ed1ng nh\u1ea5t, nh\u01b0ng khi l\u00e0m vi\u1ec7c tr\u00ean nhi\u1ec1u n\u1ec1n t\u1ea3ng, b\u1ea1n c\u1ea7n l\u01b0u \u00fd \u0111\u1ebfn:<\/em><\/p>\n\n\n\n

Kh\u1ea3 n\u0103ng h\u1ed7 tr\u1ee3 c\u00fa ph\u00e1p m\u1edf r\u1ed9ng.<\/p>\n\n\n\n

C\u00e1ch t\u1ed1i \u01b0u h\u00f3a truy v\u1ea5n.<\/p>\n\n\n\n

C\u00e1ch x\u1eed l\u00fd NULL v\u00e0 ch\u1ec9 m\u1ee5c c\u00f3 th\u1ec3 kh\u00e1c nhau \u0111\u00f4i ch\u00fat.<\/p>\n\n\n\n

Vi\u1ec7c hi\u1ec3u r\u00f5 s\u1ef1 kh\u00e1c bi\u1ec7t n\u00e0y s\u1ebd gi\u00fap b\u1ea1n vi\u1ebft truy v\u1ea5n linh ho\u1ea1t, tr\u00e1nh l\u1ed7i khi tri\u1ec3n khai h\u1ec7 th\u1ed1ng s\u1eed d\u1ee5ng \u0111a d\u1ea1ng RDBMS.<\/p>\n\n\n\n

Ph\u00e2n bi\u1ec7t INNER JOIN v\u1edbi c\u00e1c lo\u1ea1i JOIN kh\u00e1c<\/h2>\n\n\n\n

So v\u1edbi LEFT JOIN, RIGHT JOIN hay FULL OUTER JOIN, INNER JOIN ch\u1ec9 l\u1ea5y ph\u1ea7n d\u1eef li\u1ec7u giao nhau, \u0111\u1ea3m b\u1ea3o truy v\u1ea5n ch\u00ednh x\u00e1c khi c\u00f3 li\u00ean k\u1ebft h\u1ee3p l\u1ec7 gi\u1eefa c\u00e1c b\u1ea3ng.<\/p>\n\n\n\n

So s\u00e1nh INNER JOIN v\u1edbi LEFT JOIN, RIGHT JOIN v\u00e0 FULL OUTER JOIN<\/h3>\n\n\n\n

INNER JOIN, LEFT JOIN, RIGHT JOIN v\u00e0 FULL OUTER JOIN \u0111\u1ec1u l\u00e0 c\u00e1c ph\u00e9p n\u1ed1i trong SQL, nh\u01b0ng ch\u00fang kh\u00e1c nhau v\u1ec1 c\u00e1ch x\u1eed l\u00fd c\u00e1c b\u1ea3n ghi kh\u00f4ng kh\u1edbp gi\u1eefa hai b\u1ea3ng.<\/p>\n\n\n\n

Lo\u1ea1i JOIN<\/td>M\u00f4 t\u1ea3<\/td>K\u1ebft qu\u1ea3<\/td><\/tr><\/thead>
INNER JOIN<\/td>Tr\u1ea3 v\u1ec1 b\u1ea3n ghi c\u00f3 gi\u00e1 tr\u1ecb tr\u00f9ng kh\u1edbp \u1edf c\u1ea3 hai b\u1ea3ng<\/td>Ch\u1ec9 l\u1ea5y ph\u1ea7n giao nhau<\/td><\/tr>
LEFT JOIN<\/td>Tr\u1ea3 v\u1ec1 t\u1ea5t c\u1ea3 b\u1ea3n ghi t\u1eeb b\u1ea3ng b\u00ean tr\u00e1i v\u00e0 kh\u1edbp t\u1eeb b\u1ea3ng b\u00ean ph\u1ea3i (n\u1ebfu c\u00f3)<\/td>Gi\u1eef d\u1eef li\u1ec7u b\u1ea3ng tr\u00e1i<\/td><\/tr>
RIGHT JOIN<\/td>Tr\u1ea3 v\u1ec1 t\u1ea5t c\u1ea3 b\u1ea3n ghi t\u1eeb b\u1ea3ng b\u00ean ph\u1ea3i v\u00e0 kh\u1edbp t\u1eeb b\u1ea3ng b\u00ean tr\u00e1i (n\u1ebfu c\u00f3)<\/td>Gi\u1eef d\u1eef li\u1ec7u b\u1ea3ng ph\u1ea3i<\/td><\/tr>
FULL OUTER JOIN<\/td>Tr\u1ea3 v\u1ec1 t\u1ea5t c\u1ea3 b\u1ea3n ghi t\u1eeb c\u1ea3 hai b\u1ea3ng, kh\u1edbp ho\u1eb7c kh\u00f4ng kh\u1edbp<\/td>Gi\u1eef to\u00e0n b\u1ed9 d\u1eef li\u1ec7u t\u1eeb c\u1ea3 hai b\u1ea3ng<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

V\u00ed d\u1ee5:<\/p>\n\n\n\n

sql<\/p>\n\n\n\n

SELECT a.id, b.name<\/p>\n\n\n\n

FROM table_a a<\/p>\n\n\n\n

INNER JOIN table_b b ON a.id = b.id;<\/p>\n\n\n\n

\u2192 Ch\u1ec9 tr\u1ea3 v\u1ec1 b\u1ea3n ghi n\u1ebfu a.id = b.id.<\/p>\n\n\n\n

sql<\/p>\n\n\n\n

SELECT a.id, b.name<\/p>\n\n\n\n

FROM table_a a<\/p>\n\n\n\n

LEFT JOIN table_b b ON a.id = b.id;<\/p>\n\n\n\n

\u2192 Tr\u1ea3 v\u1ec1 t\u1ea5t c\u1ea3 a.id, k\u1ec3 c\u1ea3 khi kh\u00f4ng c\u00f3 b\u1ea3n ghi t\u01b0\u01a1ng \u1ee9ng trong table_b.<\/p>\n\n\n\n

Vi\u1ec7c hi\u1ec3u r\u00f5 s\u1ef1 kh\u00e1c bi\u1ec7t gi\u00fap b\u1ea1n l\u1ef1a ch\u1ecdn \u0111\u00fang lo\u1ea1i JOIN t\u00f9y theo m\u1ee5c ti\u00eau truy v\u1ea5n.<\/p>\n\n\n\n

C\u00e1c tr\u01b0\u1eddng h\u1ee3p n\u00ean ch\u1ecdn INNER JOIN thay v\u00ec JOIN m\u1eb7c \u0111\u1ecbnh<\/h3>\n\n\n\n

Trong SQL, t\u1eeb kh\u00f3a JOIN th\u01b0\u1eddng \u0111\u01b0\u1ee3c hi\u1ec3u ng\u1ea7m l\u00e0 INNER JOIN n\u1ebfu kh\u00f4ng ch\u1ec9 r\u00f5 lo\u1ea1i JOIN. Tuy nhi\u00ean, b\u1ea1n n\u00ean ch\u1ee7 \u0111\u1ed9ng s\u1eed d\u1ee5ng INNER JOIN trong c\u00e1c t\u00ecnh hu\u1ed1ng sau:<\/p>\n\n\n\n

D\u1eef li\u1ec7u y\u00eau c\u1ea7u t\u00ednh ch\u00ednh x\u00e1c cao: Ch\u1ec9 c\u1ea7n l\u1ea5y nh\u1eefng b\u1ea3n ghi c\u00f3 li\u00ean k\u1ebft \u0111\u1ea7y \u0111\u1ee7 gi\u1eefa c\u00e1c b\u1ea3ng.<\/p>\n\n\n\n

Truy v\u1ea5n c\u00f3 \u0111i\u1ec1u ki\u1ec7n r\u00f5 r\u00e0ng: Khi b\u1ea1n bi\u1ebft ch\u1eafc m\u1ed1i quan h\u1ec7 gi\u1eefa c\u00e1c b\u1ea3ng th\u00f4ng qua kh\u00f3a ch\u00ednh \u2013 kh\u00f3a ngo\u1ea1i.<\/p>\n\n\n\n

T\u1ed1i \u01b0u hi\u1ec7u su\u1ea5t: INNER JOIN th\u01b0\u1eddng c\u00f3 hi\u1ec7u su\u1ea5t t\u1ed1t h\u01a1n FULL OUTER JOIN trong h\u1ea7u h\u1ebft c\u00e1c h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u, nh\u1edd lo\u1ea1i b\u1ecf c\u00e1c b\u1ea3n ghi kh\u00f4ng li\u00ean quan.<\/p>\n\n\n\n

Tr\u00e1nh l\u1ed7i d\u1eef li\u1ec7u r\u1ed7ng (NULL): INNER JOIN lo\u1ea1i b\u1ecf c\u00e1c d\u00f2ng kh\u00f4ng c\u00f3 li\u00ean k\u1ebft, gi\u00fap k\u1ebft qu\u1ea3 truy v\u1ea5n \u201cs\u1ea1ch\u201d v\u00e0 d\u1ec5 x\u1eed l\u00fd h\u01a1n trong c\u00e1c h\u1ec7 th\u1ed1ng b\u00e1o c\u00e1o.<\/p>\n\n\n\n

S\u1eed d\u1ee5ng INNER JOIN m\u1ed9t c\u00e1ch c\u00f3 ch\u1ee7 \u0111\u00edch gi\u00fap truy v\u1ea5n tr\u1edf n\u00ean r\u00f5 r\u00e0ng, tr\u00e1nh nh\u1ea7m l\u1eabn v\u00e0 d\u1ec5 b\u1ea3o tr\u00ec trong c\u00e1c h\u1ec7 th\u1ed1ng l\u1edbn.<\/p>\n\n\n\n

C\u00e2u h\u1ecfi th\u01b0\u1eddng g\u1eb7p v\u1ec1 c\u00e1ch s\u1eed d\u1ee5ng JOIN trong SQL<\/h2>\n\n\n\n

Ng\u01b0\u1eddi h\u1ecdc th\u01b0\u1eddng th\u1eafc m\u1eafc v\u1ec1 vi\u1ec7c d\u00f9ng nhi\u1ec1u JOIN, JOIN kh\u00f4ng c\u00f3 kh\u00f3a ngo\u1ea1i, hay \u00e1p d\u1ee5ng JOIN trong c\u00e2u l\u1ec7nh UPDATE v\u00e0 DELETE trong m\u00f4i tr\u01b0\u1eddng th\u1ef1c t\u1ebf.<\/p>\n\n\n\n

C\u00f3 th\u1ec3 s\u1eed d\u1ee5ng nhi\u1ec1u JOIN trong c\u00f9ng m\u1ed9t truy v\u1ea5n kh\u00f4ng?<\/em><\/strong><\/p>\n\n\n\n

C\u00f3. B\u1ea1n ho\u00e0n to\u00e0n c\u00f3 th\u1ec3 k\u1ebft h\u1ee3p nhi\u1ec1u c\u00e2u l\u1ec7nh JOIN trong m\u1ed9t truy v\u1ea5n SQL, bao g\u1ed3m c\u1ea3 INNER JOIN, LEFT JOIN, RIGHT JOIN, ho\u1eb7c FULL OUTER JOIN n\u1ebfu h\u1ec7 qu\u1ea3n tr\u1ecb h\u1ed7 tr\u1ee3. Vi\u1ec7c n\u00e0y th\u01b0\u1eddng d\u00f9ng khi b\u1ea1n c\u1ea7n k\u1ebft n\u1ed1i ba b\u1ea3ng tr\u1edf l\u00ean. Tuy nhi\u00ean, c\u1ea7n \u0111\u1ea3m b\u1ea3o th\u1ee9 t\u1ef1 JOIN h\u1ee3p l\u00fd v\u00e0 \u0111i\u1ec1u ki\u1ec7n li\u00ean k\u1ebft r\u00f5 r\u00e0ng \u0111\u1ec3 tr\u00e1nh l\u1ed7i ho\u1eb7c d\u1eef li\u1ec7u kh\u00f4ng nh\u01b0 mong \u0111\u1ee3i.<\/p>\n\n\n\n

INNER JOIN c\u00f3 ho\u1ea1t \u0111\u1ed9ng v\u1edbi c\u00e1c b\u1ea3ng kh\u00f4ng c\u00f3 quan h\u1ec7 kh\u00f3a ngo\u1ea1i kh\u00f4ng?<\/em><\/strong><\/p>\n\n\n\n

C\u00f3 th\u1ec3. INNER JOIN kh\u00f4ng y\u00eau c\u1ea7u c\u00e1c b\u1ea3ng ph\u1ea3i c\u00f3 quan h\u1ec7 kh\u00f3a ngo\u1ea1i ch\u00ednh th\u1ee9c. \u0110i\u1ec1u quan tr\u1ecdng l\u00e0 \u0111i\u1ec1u ki\u1ec7n trong m\u1ec7nh \u0111\u1ec1 ON ph\u1ea3i h\u1ee3p l\u1ec7 v\u00e0 logic. Tuy nhi\u00ean, \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o t\u00ednh ch\u00ednh x\u00e1c v\u00e0 tr\u00e1nh truy v\u1ea5n sai l\u1ec7ch, b\u1ea1n n\u00ean s\u1eed d\u1ee5ng INNER JOIN ch\u1ee7 y\u1ebfu trong c\u00e1c b\u1ea3ng c\u00f3 quan h\u1ec7 d\u1eef li\u1ec7u r\u00f5 r\u00e0ng (ch\u1eb3ng h\u1ea1n nh\u01b0 kh\u00f3a ch\u00ednh \u2013 kh\u00f3a ngo\u1ea1i).<\/p>\n\n\n\n

C\u00f3 th\u1ec3 d\u00f9ng INNER JOIN trong c\u00e2u l\u1ec7nh UPDATE ho\u1eb7c DELETE kh\u00f4ng?<\/em><\/strong><\/p>\n\n\n\n

C\u00f3. INNER JOIN kh\u00f4ng ch\u1ec9 \u00e1p d\u1ee5ng trong truy v\u1ea5n SELECT m\u00e0 c\u00f2n c\u00f3 th\u1ec3 d\u00f9ng trong c\u00e1c c\u00e2u l\u1ec7nh UPDATE v\u00e0 DELETE khi b\u1ea1n c\u1ea7n thao t\u00e1c tr\u00ean d\u1eef li\u1ec7u li\u00ean k\u1ebft gi\u1eefa nhi\u1ec1u b\u1ea3ng. C\u00e1ch n\u00e0y th\u01b0\u1eddng d\u00f9ng \u0111\u1ec3 c\u1eadp nh\u1eadt th\u00f4ng tin c\u00f3 \u0111i\u1ec1u ki\u1ec7n ho\u1eb7c x\u00f3a d\u1eef li\u1ec7u \u0111\u1ed3ng th\u1eddi d\u1ef1a tr\u00ean li\u00ean k\u1ebft gi\u1eefa c\u00e1c b\u1ea3ng.<\/p>\n\n\n\n

Inner Join \u0111\u00f3ng vai tr\u00f2 quan tr\u1ecdng trong c\u00e1c h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7, gi\u00fap k\u1ebft n\u1ed1i d\u1eef li\u1ec7u gi\u1eefa c\u00e1c b\u1ea3ng m\u1ed9t c\u00e1ch logic v\u00e0 ch\u00ednh x\u00e1c. Khi n\u1eafm v\u1eefng c\u00e1ch ho\u1ea1t \u0111\u1ed9ng, c\u00fa ph\u00e1p v\u00e0 bi\u1ebft c\u00e1ch k\u1ebft h\u1ee3p v\u1edbi c\u00e1c m\u1ec7nh \u0111\u1ec1 nh\u01b0 WHERE<\/code>, GROUP BY<\/code> hay \u00e1p d\u1ee5ng trong UPDATE<\/code>, DELETE<\/code>, b\u1ea1n s\u1ebd ch\u1ee7 \u0111\u1ed9ng h\u01a1n trong x\u1eed l\u00fd truy v\u1ea5n. Vi\u1ec7c th\u00e0nh th\u1ea1o INNER JOIN trong SQL <\/strong>kh\u00f4ng ch\u1ec9 c\u1ea3i thi\u1ec7n hi\u1ec7u qu\u1ea3 l\u00e0m vi\u1ec7c v\u1edbi d\u1eef li\u1ec7u m\u00e0 c\u00f2n l\u00e0 n\u1ec1n t\u1ea3ng v\u1eefng ch\u1eafc \u0111\u1ec3 ph\u00e1t tri\u1ec3n trong l\u0129nh v\u1ef1c ph\u00e2n t\u00edch v\u00e0 qu\u1ea3n tr\u1ecb. H\u00e3y t\u00edch c\u1ef1c th\u1ef1c h\u00e0nh v\u00e0 ti\u1ebfp t\u1ee5c kh\u00e1m ph\u00e1 c\u00e1c lo\u1ea1i JOIN kh\u00e1c \u0111\u1ec3 n\u00e2ng cao k\u1ef9 n\u0103ng chuy\u00ean m\u00f4n.<\/p>\n\n\n\n

Tr\u00ed Nh\u00e2n<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"

L\u00e0m vi\u1ec7c v\u1edbi c\u01a1 s\u1edf d\u1eef li\u1ec7u quan h\u1ec7 kh\u00f4ng ch\u1ec9 y\u00eau c\u1ea7u hi\u1ec3u v\u1ec1 c\u1ea5u tr\u00fac b\u1ea3ng m\u00e0 c\u00f2n \u0111\u00f2i h\u1ecfi kh\u1ea3 n\u0103ng k\u1ebft …<\/p>\n","protected":false},"author":58,"featured_media":9431,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[64],"class_list":["post-9430","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-tu-van-nghe-nghiep","tag-it"],"_links":{"self":[{"href":"https:\/\/mb668s.com\/cam-nang-7mb66-xoc-dia\/wp-json\/wp\/v2\/posts\/9430","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mb668s.com\/cam-nang-7mb66-xoc-dia\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mb668s.com\/cam-nang-7mb66-xoc-dia\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mb668s.com\/cam-nang-7mb66-xoc-dia\/wp-json\/wp\/v2\/users\/58"}],"replies":[{"embeddable":true,"href":"https:\/\/mb668s.com\/cam-nang-7mb66-xoc-dia\/wp-json\/wp\/v2\/comments?post=9430"}],"version-history":[{"count":3,"href":"https:\/\/mb668s.com\/cam-nang-7mb66-xoc-dia\/wp-json\/wp\/v2\/posts\/9430\/revisions"}],"predecessor-version":[{"id":15646,"href":"https:\/\/mb668s.com\/cam-nang-7mb66-xoc-dia\/wp-json\/wp\/v2\/posts\/9430\/revisions\/15646"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/mb668s.com\/cam-nang-7mb66-xoc-dia\/wp-json\/wp\/v2\/media\/9431"}],"wp:attachment":[{"href":"https:\/\/mb668s.com\/cam-nang-7mb66-xoc-dia\/wp-json\/wp\/v2\/media?parent=9430"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mb668s.com\/cam-nang-7mb66-xoc-dia\/wp-json\/wp\/v2\/categories?post=9430"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mb668s.com\/cam-nang-7mb66-xoc-dia\/wp-json\/wp\/v2\/tags?post=9430"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}