{"id":6074,"date":"2025-12-31T18:41:23","date_gmt":"2025-12-31T11:41:23","guid":{"rendered":"https:\/\/kituaz.com\/blog\/sql-la-gi\/"},"modified":"2025-12-31T18:42:34","modified_gmt":"2025-12-31T11:42:34","slug":"sql-la-gi","status":"publish","type":"post","link":"https:\/\/kituaz.com\/blog\/sql-la-gi\/","title":{"rendered":"SQL l\u00e0 g\u00ec? T\u00ecm hi\u1ec3u v\u1ec1 ng\u00f4n ng\u1eef truy v\u1ea5n c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u1ed5 bi\u1ebfn"},"content":{"rendered":"<p>Ch\u00e0o m\u1eebng b\u1ea1n \u0111\u1ebfn v\u1edbi chuy\u00ean m\u1ee5c chia s\u1ebb c\u1ee7a KituAZ! Trong b\u00e0i vi\u1ebft n\u00e0y, ch\u00fang ta s\u1ebd kh\u00e1m ph\u00e1 v\u1ec1 SQL &#8211; m\u1ed9t ng\u00f4n ng\u1eef truy v\u1ea5n c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u1ed5 bi\u1ebfn. SQL \u0111\u00f3ng vai tr\u00f2 quan tr\u1ecdng trong qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 cung c\u1ea5p kh\u1ea3 n\u0103ng truy xu\u1ea5t d\u1eef li\u1ec7u hi\u1ec7u qu\u1ea3. H\u00e3y c\u00f9ng t\u00ecm hi\u1ec3u v\u1ec1 SQL v\u00e0 nh\u1eefng l\u1ee3i \u00edch m\u00e0 n\u00f3 mang l\u1ea1<\/p>\n<h2>FAQ<\/h2>\n<h3>SQL l\u00e0 g\u00ec?<\/h3>\n<p>SQL (Structured Query Language) l\u00e0 m\u1ed9t ng\u00f4n ng\u1eef l\u1eadp tr\u00ecnh \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 truy v\u1ea5n, qu\u1ea3n l\u00fd v\u00e0 t\u01b0\u01a1ng t\u00e1c v\u1edbi c\u01a1 s\u1edf d\u1eef li\u1ec7u. N\u00f3 cho ph\u00e9p ch\u00fang ta truy v\u1ea5n d\u1eef li\u1ec7u, t\u1ea1o b\u1ea3ng, th\u00eam, s\u1eeda \u0111\u1ed5i v\u00e0 x\u00f3a d\u1eef li\u1ec7u, c\u0169ng nh\u01b0 th\u1ef1c hi\u1ec7n c\u00e1c thao t\u00e1c ph\u1ee9c t\u1ea1p nh\u01b0 k\u1ebft h\u1ee3p, nh\u00f3m v\u00e0 s\u1eafp x\u1ebfp d\u1eef li\u1ec7u.<\/p>\n<h3>SQL ho\u1ea1t \u0111\u1ed9ng nh\u01b0 th\u1ebf n\u00e0o?<\/h3>\n<p>SQL ho\u1ea1t \u0111\u1ed9ng b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng c\u00e1c c\u00e2u l\u1ec7nh \u0111\u1ec3 truy v\u1ea5n v\u00e0 t\u01b0\u01a1ng t\u00e1c v\u1edbi c\u01a1 s\u1edf d\u1eef li\u1ec7u. Ch\u00fang ta c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng c\u00e1c c\u00e2u l\u1ec7nh SELECT \u0111\u1ec3 truy v\u1ea5n d\u1eef li\u1ec7u t\u1eeb b\u1ea3ng, c\u00e2u l\u1ec7nh INSERT \u0111\u1ec3 th\u00eam d\u1eef li\u1ec7u v\u00e0o b\u1ea3ng, c\u00e2u l\u1ec7nh UPDATE \u0111\u1ec3 c\u1eadp nh\u1eadt d\u1eef li\u1ec7u v\u00e0 c\u00e2u l\u1ec7nh DELETE \u0111\u1ec3 x\u00f3a d\u1eef li\u1ec7u. SQL c\u00f3 c\u00fa ph\u00e1p \u0111\u01a1n gi\u1ea3n v\u00e0 d\u1ec5 hi\u1ec3u, gi\u00fap ch\u00fang ta l\u00e0m vi\u1ec7c v\u1edbi c\u01a1 s\u1edf d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch d\u1ec5 d\u00e0ng.<\/p>\n<h3>L\u1ee3i \u00edch c\u1ee7a vi\u1ec7c s\u1eed d\u1ee5ng SQL l\u00e0 g\u00ec?<\/h3>\n<p>SQL mang l\u1ea1i nhi\u1ec1u l\u1ee3i \u00edch \u0111\u00e1ng k\u1ec3 trong qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u, bao g\u1ed3m:<\/p>\n<ul>\n<li>Qu\u1ea3n l\u00fd v\u00e0 t\u1ed5 ch\u1ee9c d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3: SQL cho ph\u00e9p ch\u00fang ta t\u1ea1o b\u1ea3ng, qu\u1ea3n l\u00fd quan h\u1ec7 gi\u1eefa c\u00e1c b\u1ea3ng v\u00e0 \u0111\u1ecbnh d\u1ea1ng d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch ch\u00ednh x\u00e1c.<\/li>\n<li>C\u1ea3i thi\u1ec7n b\u1ea3o m\u1eadt v\u00e0 t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u: SQL cung c\u1ea5p c\u00e1c t\u00ednh n\u0103ng b\u1ea3o m\u1eadt nh\u01b0 ph\u00e2n quy\u1ec1n truy c\u1eadp v\u00e0 m\u00e3 h\u00f3a d\u1eef li\u1ec7u, \u0111\u1ea3m b\u1ea3o an to\u00e0n cho c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/li>\n<li>D\u1ec5 d\u00e0ng truy xu\u1ea5t v\u00e0 ph\u00e2n t\u00edch d\u1eef li\u1ec7u: SQL cho ph\u00e9p ch\u00fang ta truy v\u1ea5n d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch linh ho\u1ea1t v\u00e0 nhanh ch\u00f3ng, t\u1eeb \u0111\u00f3 gi\u00fap ch\u00fang ta t\u00ecm ra th\u00f4ng tin c\u1ea7n thi\u1ebft v\u00e0 ph\u00e2n t\u00edch d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3.<\/li>\n<li>T\u00ednh m\u1edf r\u1ed9ng v\u00e0 kh\u1ea3 n\u0103ng h\u1ee3p t\u00e1c: SQL l\u00e0 m\u1ed9t ng\u00f4n ng\u1eef chu\u1ea9n, \u0111\u01b0\u1ee3c h\u1ed7 tr\u1ee3 b\u1edfi nhi\u1ec1u h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u kh\u00e1c nhau, cho ph\u00e9p ch\u00fang ta d\u1ec5 d\u00e0ng m\u1edf r\u1ed9ng v\u00e0 chia s\u1ebb d\u1eef li\u1ec7u gi\u1eefa c\u00e1c \u1ee9ng d\u1ee5ng v\u00e0 h\u1ec7 th\u1ed1ng kh\u00e1c nhau.<\/li>\n<\/ul>\n<h3>SQL c\u00f3 d\u1ec5 h\u1ecdc kh\u00f4ng?<\/h3>\n<p>SQL c\u00f3 c\u00fa ph\u00e1p \u0111\u01a1n gi\u1ea3n v\u00e0 d\u1ec5 hi\u1ec3u, \u0111i\u1ec1u n\u00e0y l\u00e0m cho n\u00f3 tr\u1edf th\u00e0nh m\u1ed9t ng\u00f4n ng\u1eef d\u1ec5 h\u1ecdc cho ng\u01b0\u1eddi m\u1edbi b\u1eaft \u0111\u1ea7u. B\u1ea1n kh\u00f4ng c\u1ea7n c\u00f3 ki\u1ebfn th\u1ee9c l\u1eadp tr\u00ecnh s\u00e2u, ch\u1ec9 c\u1ea7n hi\u1ec3u c\u00e1ch s\u1eed d\u1ee5ng c\u00e1c c\u00e2u l\u1ec7nh c\u01a1 b\u1ea3n v\u00e0 th\u1ef1c h\u00e0nh s\u1ebd gi\u00fap b\u1ea1n n\u1eafm b\u1eaft \u0111\u01b0\u1ee3c SQL m\u1ed9t c\u00e1ch nhanh ch\u00f3ng.<\/p>\n<h2>Gi\u1edbi thi\u1ec7u v\u1ec1 SQL<\/h2>\n<p>SQL (Structured Query Language) l\u00e0 m\u1ed9t ng\u00f4n ng\u1eef l\u1eadp tr\u00ecnh ph\u1ed5 bi\u1ebfn \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u. V\u1edbi SQL, ch\u00fang ta c\u00f3 th\u1ec3 t\u1ea1o, truy v\u1ea5n v\u00e0 qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3. SQL \u0111\u01b0\u1ee3c ph\u00e1t tri\u1ec3n t\u1eeb ng\u00f4n ng\u1eef SEQUEL (Structured English Query Language) v\u00e0o nh\u1eefng n\u0103m 1970 b\u1edfi c\u00e1c nh\u00e0 khoa h\u1ecdc c\u1ee7a IBM v\u00e0 sau \u0111\u00f3 \u0111\u00e3 tr\u1edf th\u00e0nh chu\u1ea9n ng\u00e0nh c\u00f4ng nghi\u1ec7p.<\/p>\n<p>SQL ch\u1ee7 y\u1ebfu s\u1eed d\u1ee5ng \u0111\u1ec3 l\u00e0m vi\u1ec7c v\u1edbi c\u00e1c h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u (DBMS) nh\u01b0 MySQL, Oracle, MS SQL Server v\u00e0 PostgreSQL. V\u1edbi SQL, ch\u00fang ta c\u00f3 th\u1ec3 truy v\u1ea5n d\u1eef li\u1ec7u t\u1eeb c\u01a1 s\u1edf d\u1eef li\u1ec7u, t\u1ea1o b\u1ea3ng, th\u00eam, s\u1eeda \u0111\u1ed5i v\u00e0 x\u00f3a d\u1eef li\u1ec7u, c\u0169ng nh\u01b0 th\u1ef1c hi\u1ec7n c\u00e1c thao t\u00e1c ph\u1ee9c t\u1ea1p nh\u01b0 k\u1ebft h\u1ee3p, nh\u00f3m v\u00e0 s\u1eafp x\u1ebfp d\u1eef li\u1ec7u.<\/p>\n<p>SQL \u0111\u00f3ng vai tr\u00f2 quan tr\u1ecdng trong vi\u1ec7c qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 cung c\u1ea5p kh\u1ea3 n\u0103ng truy xu\u1ea5t d\u1eef li\u1ec7u hi\u1ec7u qu\u1ea3. V\u1edbi SQL, ch\u00fang ta c\u00f3 th\u1ec3 d\u1ec5 d\u00e0ng t\u01b0\u01a1ng t\u00e1c v\u1edbi c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 t\u00ecm ra th\u00f4ng tin c\u1ea7n thi\u1ebft m\u1ed9t c\u00e1ch nhanh ch\u00f3ng.<\/p>\n<h2>C\u00e1ch SQL ho\u1ea1t \u0111\u1ed9ng<\/h2>\n<p>SQL ho\u1ea1t \u0111\u1ed9ng b\u1eb1ng c\u00e1ch s\u1eed d\u1ee5ng c\u00e1c c\u00e2u l\u1ec7nh \u0111\u1ec3 truy v\u1ea5n v\u00e0 t\u01b0\u01a1ng t\u00e1c v\u1edbi c\u01a1 s\u1edf d\u1eef li\u1ec7u. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 m\u1ed9t s\u1ed1 kh\u00e1i ni\u1ec7m c\u01a1 b\u1ea3n v\u1ec1 c\u00e1ch SQL ho\u1ea1t \u0111\u1ed9ng:<\/p>\n<h3>C\u00fa ph\u00e1p v\u00e0 c\u1ea5u tr\u00fac SQL<\/h3>\n<p>SQL s\u1eed d\u1ee5ng c\u00fa ph\u00e1p \u0111\u01a1n gi\u1ea3n v\u00e0 d\u1ec5 hi\u1ec3u, gi\u00fap ch\u00fang ta l\u00e0m vi\u1ec7c v\u1edbi c\u01a1 s\u1edf d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch d\u1ec5 d\u00e0ng. C\u00e2u l\u1ec7nh SQL th\u01b0\u1eddng \u0111\u01b0\u1ee3c vi\u1ebft d\u01b0\u1edbi d\u1ea1ng v\u0103n b\u1ea3n v\u00e0 chia th\u00e0nh nhi\u1ec1u ph\u1ea7n nh\u1ecf nh\u01b0 SELECT, FROM, WHERE, v\u00e0 ORDER BY. V\u00ed d\u1ee5:<\/p>\n<pre><code>SELECT * FROM customers WHERE country = 'Vietnam' ORDER BY last_name;<\/code><\/pre>\n<p>Trong c\u00e2u l\u1ec7nh tr\u00ean, ch\u00fang ta \u0111ang truy v\u1ea5n t\u1ea5t c\u1ea3 c\u00e1c kh\u00e1ch h\u00e0ng t\u1eeb b\u1ea3ng &#8220;customers&#8221; c\u00f3 qu\u1ed1c gia l\u00e0 &#8220;Vietnam&#8221; v\u00e0 s\u1eafp x\u1ebfp k\u1ebft qu\u1ea3 theo h\u1ecd.<\/p>\n<h3>C\u00e2u l\u1ec7nh v\u00e0 truy v\u1ea5n SQL<\/h3>\n<p>SQL s\u1eed d\u1ee5ng c\u00e1c c\u00e2u l\u1ec7nh \u0111\u1ec3 th\u1ef1c hi\u1ec7n c\u00e1c thao t\u00e1c tr\u00ean c\u01a1 s\u1edf d\u1eef li\u1ec7u. C\u00e1c c\u00e2u l\u1ec7nh ph\u1ed5 bi\u1ebfn nh\u1ea5t trong SQL bao g\u1ed3m:<\/p>\n<ul>\n<li>SELECT: Truy v\u1ea5n d\u1eef li\u1ec7u t\u1eeb c\u01a1 s\u1edf d\u1eef li\u1ec7u.<\/li>\n<li>INSERT: Th\u00eam d\u1eef li\u1ec7u v\u00e0o b\u1ea3ng.<\/li>\n<li>UPDATE: C\u1eadp nh\u1eadt d\u1eef li\u1ec7u trong b\u1ea3ng.<\/li>\n<li>DELETE: X\u00f3a d\u1eef li\u1ec7u t\u1eeb b\u1ea3ng.<\/li>\n<\/ul>\n<p>V\u00ed d\u1ee5, c\u00e2u l\u1ec7nh SELECT \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 truy v\u1ea5n d\u1eef li\u1ec7u t\u1eeb c\u01a1 s\u1edf d\u1eef li\u1ec7u:<\/p>\n<pre><code>SELECT * FROM customers;<\/code><\/pre>\n<p>C\u00e2u l\u1ec7nh tr\u00ean s\u1ebd tr\u1ea3 v\u1ec1 t\u1ea5t c\u1ea3 c\u00e1c h\u00e0ng trong b\u1ea3ng &#8220;customers&#8221;.<\/p>\n<h3>C\u00e1c c\u00e2u l\u1ec7nh v\u00e0 ch\u1ee9c n\u0103ng SQL th\u00f4ng d\u1ee5ng<\/h3>\n<p>SQL cung c\u1ea5p nhi\u1ec1u c\u00e2u l\u1ec7nh v\u00e0 ch\u1ee9c n\u0103ng kh\u00e1c nhau \u0111\u1ec3 l\u00e0m vi\u1ec7c v\u1edbi d\u1eef li\u1ec7u. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 m\u1ed9t s\u1ed1 c\u00e2u l\u1ec7nh v\u00e0 ch\u1ee9c n\u0103ng SQL th\u00f4ng d\u1ee5ng:<\/p>\n<ul>\n<li>DISTINCT: Lo\u1ea1i b\u1ecf c\u00e1c gi\u00e1 tr\u1ecb tr\u00f9ng l\u1eb7p trong k\u1ebft qu\u1ea3 truy v\u1ea5n.<\/li>\n<li>WHERE: L\u1ecdc d\u1eef li\u1ec7u d\u1ef1a tr\u00ean m\u1ed9t \u0111i\u1ec1u ki\u1ec7n c\u1ee5 th\u1ec3.<\/li>\n<li>JOIN: K\u1ebft h\u1ee3p d\u1eef li\u1ec7u t\u1eeb hai ho\u1eb7c nhi\u1ec1u b\u1ea3ng d\u1ef1a tr\u00ean m\u1ed9t \u0111i\u1ec1u ki\u1ec7n li\u00ean k\u1ebft.<\/li>\n<li>GROUP BY: Nh\u00f3m d\u1eef li\u1ec7u d\u1ef1a tr\u00ean m\u1ed9t c\u1ed9t c\u1ee5 th\u1ec3.<\/li>\n<li>ORDER BY: S\u1eafp x\u1ebfp k\u1ebft qu\u1ea3 truy v\u1ea5n theo m\u1ed9t ho\u1eb7c nhi\u1ec1u c\u1ed9t.<\/li>\n<li>COUNT, SUM, AVG, MAX, MIN: T\u00ednh to\u00e1n d\u1eef li\u1ec7u trong c\u1ed9t d\u1ef1a tr\u00ean m\u1ed9t \u0111i\u1ec1u ki\u1ec7n.<\/li>\n<\/ul>\n<h3>Truy xu\u1ea5t v\u00e0 x\u1eed l\u00fd d\u1eef li\u1ec7u trong SQL<\/h3>\n<p>SQL cho ph\u00e9p ch\u00fang ta truy xu\u1ea5t v\u00e0 x\u1eed l\u00fd d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch linh ho\u1ea1t. Ch\u00fang ta c\u00f3 th\u1ec3 truy v\u1ea5n d\u1eef li\u1ec7u t\u1eeb m\u1ed9t ho\u1eb7c nhi\u1ec1u b\u1ea3ng, \u00e1p d\u1ee5ng c\u00e1c \u0111i\u1ec1u ki\u1ec7n l\u1ecdc v\u00e0 th\u1ef1c hi\u1ec7n c\u00e1c thao t\u00e1c t\u00ednh to\u00e1n. V\u00ed d\u1ee5, ch\u00fang ta c\u00f3 th\u1ec3 t\u00ednh t\u1ed5ng s\u1ed1 s\u1ea3n ph\u1ea9m \u0111\u00e3 b\u00e1n trong m\u1ed9t th\u00e1ng nh\u01b0 sau:<\/p>\n<pre><code>SELECT SUM(quantity) FROM orders WHERE MONTH(order_date) = 10;<\/code><\/pre>\n<p>C\u00e2u l\u1ec7nh tr\u00ean s\u1ebd t\u00ednh t\u1ed5ng s\u1ed1 l\u01b0\u1ee3ng s\u1ea3n ph\u1ea9m \u0111\u00e3 b\u00e1n trong th\u00e1ng 10 t\u1eeb b\u1ea3ng &#8220;orders&#8221;.<\/p>\n<h2>L\u1ee3i \u00edch c\u1ee7a vi\u1ec7c s\u1eed d\u1ee5ng SQL<\/h2>\n<p>SQL mang l\u1ea1i nhi\u1ec1u l\u1ee3i \u00edch quan tr\u1ecdng trong qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u. D\u01b0\u1edbi \u0111\u00e2y l\u00e0 m\u1ed9t s\u1ed1 l\u1ee3i \u00edch ch\u00ednh c\u1ee7a vi\u1ec7c s\u1eed d\u1ee5ng SQL:<\/p>\n<h3>Qu\u1ea3n l\u00fd v\u00e0 t\u1ed5 ch\u1ee9c d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3<\/h3>\n<p>SQL cho ph\u00e9p ch\u00fang ta t\u1ea1o b\u1ea3ng, qu\u1ea3n l\u00fd quan h\u1ec7 gi\u1eefa c\u00e1c b\u1ea3ng v\u00e0 \u0111\u1ecbnh d\u1ea1ng d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch ch\u00ednh x\u00e1c. Ch\u00fang ta c\u00f3 th\u1ec3 x\u00e1c \u0111\u1ecbnh ki\u1ec3u d\u1eef li\u1ec7u cho m\u1ed7i c\u1ed9t, thi\u1ebft l\u1eadp r\u00e0ng bu\u1ed9c v\u00e0 quy \u0111\u1ecbnh quan h\u1ec7 gi\u1eefa c\u00e1c b\u1ea3ng. SQL cung c\u1ea5p c\u00e1c c\u00f4ng c\u1ee5 \u0111\u1ec3 qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch hi\u1ec7u qu\u1ea3 v\u00e0 gi\u00fap ch\u00fang ta t\u1ed5 ch\u1ee9c d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch logic.<\/p>\n<h3>C\u1ea3i thi\u1ec7n b\u1ea3o m\u1eadt v\u00e0 t\u00ednh to\u00e0n v\u1eb9n d\u1eef li\u1ec7u<\/h3>\n<p>SQL cung c\u1ea5p c\u00e1c t\u00ednh n\u0103ng b\u1ea3o m\u1eadt nh\u01b0 ph\u00e2n quy\u1ec1n truy c\u1eadp v\u00e0 m\u00e3 h\u00f3a d\u1eef li\u1ec7u, \u0111\u1ea3m b\u1ea3o an to\u00e0n cho c\u01a1 s\u1edf d\u1eef li\u1ec7u. Ch\u00fang ta c\u00f3 th\u1ec3 thi\u1ebft l\u1eadp quy\u1ec1n truy c\u1eadp cho ng\u01b0\u1eddi d\u00f9ng v\u00e0 nh\u00f3m ng\u01b0\u1eddi d\u00f9ng, t\u1eeb \u0111\u00f3 ki\u1ec3m so\u00e1t quy\u1ec1n truy c\u1eadp v\u00e0o d\u1eef li\u1ec7u. SQL c\u0169ng h\u1ed7 tr\u1ee3 m\u00e3 h\u00f3a d\u1eef li\u1ec7u \u0111\u1ec3 \u0111\u1ea3m b\u1ea3o t\u00ednh to\u00e0n v\u1eb9n v\u00e0 b\u1ea3o m\u1eadt c\u1ee7a d\u1eef li\u1ec7u.<\/p>\n<h3>D\u1ec5 d\u00e0ng truy xu\u1ea5t v\u00e0 ph\u00e2n t\u00edch d\u1eef li\u1ec7u<\/h3>\n<p>SQL cho ph\u00e9p ch\u00fang ta truy v\u1ea5n d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch linh ho\u1ea1t v\u00e0 nhanh ch\u00f3ng. Ch\u00fang ta c\u00f3 th\u1ec3 s\u1eed d\u1ee5ng c\u00e1c c\u00e2u l\u1ec7nh SELECT \u0111\u1ec3 truy xu\u1ea5t d\u1eef li\u1ec7u t\u1eeb m\u1ed9t ho\u1eb7c nhi\u1ec1u b\u1ea3ng, \u00e1p d\u1ee5ng c\u00e1c \u0111i\u1ec1u ki\u1ec7n l\u1ecdc v\u00e0 s\u1eafp x\u1ebfp k\u1ebft qu\u1ea3 theo mong mu\u1ed1n. SQL c\u0169ng cung c\u1ea5p c\u00e1c ch\u1ee9c n\u0103ng t\u00ednh to\u00e1n nh\u01b0 COUNT, SUM, AVG, MAX v\u00e0 MIN \u0111\u1ec3 ph\u00e2n t\u00edch d\u1eef li\u1ec7u.<\/p>\n<h3>T\u00ednh m\u1edf r\u1ed9ng v\u00e0 kh\u1ea3 n\u0103ng h\u1ee3p t\u00e1c<\/h3>\n<p>SQL l\u00e0 m\u1ed9t ng\u00f4n ng\u1eef chu\u1ea9n, \u0111\u01b0\u1ee3c h\u1ed7 tr\u1ee3 b\u1edfi nhi\u1ec1u h\u1ec7 qu\u1ea3n tr\u1ecb c\u01a1 s\u1edf d\u1eef li\u1ec7u kh\u00e1c nhau. \u0110i\u1ec1u n\u00e0y cho ph\u00e9p ch\u00fang ta d\u1ec5 d\u00e0ng m\u1edf r\u1ed9ng v\u00e0 chia s\u1ebb d\u1eef li\u1ec7u gi\u1eefa c\u00e1c \u1ee9ng d\u1ee5ng v\u00e0 h\u1ec7 th\u1ed1ng kh\u00e1c nhau. SQL c\u0169ng h\u1ed7 tr\u1ee3 c\u00e1c t\u00ednh n\u0103ng nh\u01b0 giao d\u1ecbch v\u00e0 \u0111a ng\u01b0\u1eddi d\u00f9ng, cho ph\u00e9p nhi\u1ec1u ng\u01b0\u1eddi d\u00f9ng c\u00f9ng truy c\u1eadp v\u00e0 l\u00e0m vi\u1ec7c tr\u00ean c\u00f9ng m\u1ed9t c\u01a1 s\u1edf d\u1eef li\u1ec7u m\u1ed9t c\u00e1ch an to\u00e0n.<\/p>\n<h2>K\u1ebft lu\u1eadn<\/h2>\n<p>Trong b\u00e0i vi\u1ebft n\u00e0y, ch\u00fang ta \u0111\u00e3 t\u00ecm hi\u1ec3u v\u1ec1 SQL &#8211; m\u1ed9t ng\u00f4n ng\u1eef truy v\u1ea5n c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u1ed5 bi\u1ebfn. SQL \u0111\u00f3ng vai tr\u00f2 quan tr\u1ecdng trong qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 cung c\u1ea5p kh\u1ea3 n\u0103ng truy xu\u1ea5t d\u1eef li\u1ec7u hi\u1ec7u qu\u1ea3. Ch\u00fang ta \u0111\u00e3 kh\u00e1m ph\u00e1 c\u00e1ch SQL ho\u1ea1t \u0111\u1ed9ng, c\u00e1c c\u00e2u l\u1ec7nh v\u00e0 ch\u1ee9c n\u0103ng SQL th\u00f4ng d\u1ee5ng, c\u0169ng nh\u01b0 l\u1ee3i \u00edch c\u1ee7a vi\u1ec7c s\u1eed d\u1ee5ng SQL.<\/p>\n<p>D\u1ec5 d\u00e0ng h\u1ecdc, hi\u1ec7u qu\u1ea3 trong qu\u1ea3n l\u00fd d\u1eef li\u1ec7u v\u00e0 cung c\u1ea5p kh\u1ea3 n\u0103ng truy xu\u1ea5t linh ho\u1ea1t, SQL l\u00e0 m\u1ed9t ng\u00f4n ng\u1eef kh\u00f4ng th\u1ec3 thi\u1ebfu \u0111\u1ed1i v\u1edbi c\u00e1c chuy\u00ean gia qu\u1ea3n l\u00fd c\u01a1 s\u1edf d\u1eef li\u1ec7u v\u00e0 nh\u00e0 ph\u00e1t tri\u1ec3n ph\u1ea7n m\u1ec1m. H\u00e3y b\u1eaft \u0111\u1ea7u h\u1ecdc SQL ngay h\u00f4m nay v\u00e0 kh\u00e1m ph\u00e1 s\u1ee9c m\u1ea1nh c\u1ee7a n\u00f3 trong vi\u1ec7c l\u00e0m vi\u1ec7c v\u1edbi c\u01a1 s\u1edf d\u1eef li\u1ec7u!<\/p>\n<p><em>\u0110\u0103ng b\u00e0i vi\u1ebft n\u00e0y tr\u00ean KituAZ Blog &#8211; n\u01a1i chia s\u1ebb ki\u1ebfn th\u1ee9c v\u00e0 gi\u1ea3i \u0111\u00e1p c\u00e1c c\u00e2u h\u1ecfi th\u01b0\u1eddng g\u1eb7p trong cu\u1ed9c s\u1ed1ng. T\u1ea1i \u0111\u00e2y, b\u1ea1n c\u00f3 th\u1ec3 t\u00ecm l\u1eddi gi\u1ea3i \u0111\u00e1p cho c\u00e1c kh\u00e1i ni\u1ec7m, c\u00e2u h\u1ecfi v\u00e0 th\u1eafc m\u1eafc m\u00e0 b\u1ea1n \u0111ang g\u1eb7p ph\u1ea3H\u00e3y truy c\u1eadp <a href=\"https:\/\/kituaz.com\/blog\/chia-se\/\">\u0111\u00e2y<\/a> \u0111\u1ec3 kh\u00e1m ph\u00e1 th\u00eam nhi\u1ec1u b\u00e0i vi\u1ebft h\u1eefu \u00edch kh\u00e1c.<\/em><\/p>\n\n\n<div class=\"kk-star-ratings kksr-auto kksr-align-right kksr-valign-bottom\"\n    data-payload='{&quot;align&quot;:&quot;right&quot;,&quot;id&quot;:&quot;6074&quot;,&quot;slug&quot;:&quot;default&quot;,&quot;valign&quot;:&quot;bottom&quot;,&quot;ignore&quot;:&quot;&quot;,&quot;reference&quot;:&quot;auto&quot;,&quot;class&quot;:&quot;&quot;,&quot;count&quot;:&quot;0&quot;,&quot;legendonly&quot;:&quot;&quot;,&quot;readonly&quot;:&quot;&quot;,&quot;score&quot;:&quot;0&quot;,&quot;starsonly&quot;:&quot;&quot;,&quot;best&quot;:&quot;5&quot;,&quot;gap&quot;:&quot;4&quot;,&quot;greet&quot;:&quot;&quot;,&quot;legend&quot;:&quot;0\\\/5 - (0 b\u00ecnh ch\u1ecdn)&quot;,&quot;size&quot;:&quot;24&quot;,&quot;title&quot;:&quot;SQL l\u00e0 g\u00ec? T\u00ecm hi\u1ec3u v\u1ec1 ng\u00f4n ng\u1eef truy v\u1ea5n c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u1ed5 bi\u1ebfn&quot;,&quot;width&quot;:&quot;0&quot;,&quot;_legend&quot;:&quot;{score}\\\/{best} - ({count} {votes})&quot;,&quot;font_factor&quot;:&quot;1.25&quot;}'>\n            \n<div class=\"kksr-stars\">\n    \n<div class=\"kksr-stars-inactive\">\n            <div class=\"kksr-star\" data-star=\"1\" style=\"padding-right: 4px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" data-star=\"2\" style=\"padding-right: 4px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" data-star=\"3\" style=\"padding-right: 4px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" data-star=\"4\" style=\"padding-right: 4px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" data-star=\"5\" style=\"padding-right: 4px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n    <\/div>\n    \n<div class=\"kksr-stars-active\" style=\"width: 0px;\">\n            <div class=\"kksr-star\" style=\"padding-right: 4px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" style=\"padding-right: 4px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" style=\"padding-right: 4px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" style=\"padding-right: 4px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n            <div class=\"kksr-star\" style=\"padding-right: 4px\">\n            \n\n<div class=\"kksr-icon\" style=\"width: 24px; height: 24px;\"><\/div>\n        <\/div>\n    <\/div>\n<\/div>\n                \n\n<div class=\"kksr-legend\" style=\"font-size: 19.2px;\">\n            <span class=\"kksr-muted\"><\/span>\n    <\/div>\n    <\/div>\n","protected":false},"excerpt":{"rendered":"<p>T\u00ecm hi\u1ec3u v\u1ec1 SQL &#8211; ng\u00f4n ng\u1eef truy v\u1ea5n c\u01a1 s\u1edf d\u1eef li\u1ec7u ph\u1ed5 bi\u1ebfn. SQL l\u00e0 g\u00ec? H\u01b0\u1edbng d\u1eabn t\u1eeb A-Z v\u1ec1 c\u00fa ph\u00e1p, l\u1ee3i \u00edch v\u00e0 c\u00e1ch l\u00e0m vi\u1ec7c v\u1edbi SQL.<\/p>\n","protected":false},"author":1,"featured_media":6075,"parent":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[],"class_list":["post-6074","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-chia-se"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.3 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>SQL l\u00e0 g\u00ec? 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