\u76ee\u5f55<\/p>\n
1. \u4ec0\u4e48\u662f SQL<\/p>\n
2. \u73af\u5883\u51c6\u5907（\u65b0\u624b\u63a8\u8350）<\/p>\n
\u4e8c\u3001SQL \u5165\u95e8：\u6838\u5fc3\u8bed\u6cd5（CRUD）<\/p>\n
1. \u6570\u636e\u5e93\u4e0e\u8868\u64cd\u4f5c（DDL）<\/p>\n
2. \u6570\u636e\u64cd\u4f5c（DML）：\u589e\u5220\u6539<\/p>\n
3. \u6570\u636e\u67e5\u8be2（DQL）：\u6700\u6838\u5fc3\u7684 SELECT<\/p>\n
（1）\u57fa\u7840\u67e5\u8be2<\/p>\n
（2）\u6761\u4ef6\u67e5\u8be2（WHERE）<\/p>\n
（3）\u6392\u5e8f（ORDER BY）<\/p>\n
（4）\u805a\u5408\u51fd\u6570<\/p>\n
（5）\u5206\u7ec4\u67e5\u8be2（GROUP BY）<\/p>\n
（6）\u5206\u9875\u67e5\u8be2<\/p>\n
\u4e09\u3001SQL \u8fdb\u9636：\u591a\u8868\u64cd\u4f5c\u4e0e\u9ad8\u7ea7\u8bed\u6cd5<\/p>\n
1. \u591a\u8868\u8fde\u63a5（JOIN）<\/p>\n
\u6838\u5fc3\u8fde\u63a5\u7c7b\u578b：<\/p>\n
2. \u5b50\u67e5\u8be2<\/p>\n
3. \u5e38\u7528\u9ad8\u7ea7\u8bed\u6cd5<\/p>\n
（1）CASE WHEN：\u6761\u4ef6\u5206\u652f<\/p>\n
（2）\u4e8b\u52a1（TRANSACTION）<\/p>\n
（3）\u7d22\u5f15（INDEX）<\/p>\n
\u56db\u3001SQL \u4f18\u5316（\u8fdb\u9636\u5fc5\u5907）<\/p>\n
\u4e94\u3001\u5b9e\u6218\u7ec3\u4e60<\/p>\n
\u603b\u7ed3<\/p>\n
SQL\u8bed\u53e5\u662f\u64cd\u4f5c\u6570\u636e\u5e93\u7684\u6838\u5fc3，\u65e0\u8bba\u662fMysql\u3001PostgreSQL\u3001SQL Server\u3001Oracle\u90fd\u9700\u8981\u901a\u8fc7SQL\u8bed\u53e5\u8fdb\u884c\u64cd\u4f5c\u3002\u56e0\u6b64，\u53ea\u8981\u638c\u63e1\u4e86SQL\u8bed\u53e5，\u4eca\u540e\u4e0d\u8bba\u9047\u5230\u4ec0\u4e48\u7c7b\u578b\u7684\u5173\u7cfb\u578b\u6570\u636e\u5e93\u90fd\u80fd\u5229\u7528SQL\u8bed\u53e5\u8fdb\u884c\u589e\u5220\u6539\u67e5\u3002<\/p>\n
\u5728\u5b66\u4e60SQL\u8bed\u53e5\u4e4b\u524d，\u6211\u4eec\u5148\u6765\u4e86\u89e3\u4e00\u4e0b\u4ec0\u4e48\u662fSQL\u8bed\u53e5\u3002<\/p>\n
SQL（Structured Query Language）\u662f\u7ed3\u6784\u5316\u67e5\u8be2\u8bed\u8a00，\u7528\u4e8e\u7ba1\u7406\u548c\u64cd\u4f5c\u5173\u7cfb\u578b\u6570\u636e\u5e93（\u5982 MySQL\u3001PostgreSQL\u3001SQL Server\u3001Oracle），\u6838\u5fc3\u80fd\u529b\u5305\u62ec：<\/p>\n
\u7b80\u5355\u6765\u8bf4：SQL\u662f\u4e00\u79cd\u7528\u4e8e\u64cd\u4f5c\u5173\u7cfb\u578b\u6570\u636e\u5e93\u7684\u8bed\u8a00\u3002\u5982\u540cjava\u548cC++\u7f16\u5199\u7a0b\u5e8f\u4e00\u6837，SQL\u4e0d\u540c\u7684\u70b9\u5728\u4e8e\u64cd\u4f5c\u6570\u636e\u5e93\u3002\u5982\u679c\u8bfb\u8005\u6709\u9ad8\u7ea7\u7f16\u7a0b\u8bed\u8a00\u7684\u57fa\u7840\u7684\u8bdd，\u5bf9\u4e8eSQL\u8bed\u53e5\u7684\u5b66\u4e60\u4f1a\u66f4\u52a0\u5f97\u5fc3\u5e94\u624b\u3002<\/p>\n
\u4e0b\u9762\u662f\u4e00\u4e9b\u5e38\u89c1\u7684SQL\u8bed\u53e5，\u80fd\u591f\u5e2e\u52a9\u4f60\u4ece0\u52301\u638c\u63e1SQL\u8bed\u53e5\u3002（SQL\u8bed\u53e5\u4e0d\u533a\u5206\u5927\u5c0f\u5199，\u5373\u5bf9\u5927\u5c0f\u5199\u4e0d\u654f\u611f，\u56e0\u6b64\u4ee5\u4e0b\u5927\u5199\u5b57\u6bcd\u5747\u53ef\u4ee5\u6539\u4e3a\u5c0f\u5199）<\/p>\n
\u5148\u638c\u63e1\u5982\u4f55\u521b\u5efa \/ \u67e5\u770b \/ \u5220\u9664\u6570\u636e\u5e93\u548c\u8868，\u8fd9\u662f\u64cd\u4f5c\u6570\u636e\u7684\u57fa\u7840\u3002<\/p>\n
— 1. \u6570\u636e\u5e93\u64cd\u4f5c
\nCREATE DATABASE IF NOT EXISTS test_db; — \u521b\u5efa\u6570\u636e\u5e93（\u907f\u514d\u91cd\u590d）
\nUSE test_db; — \u5207\u6362\u5230\u76ee\u6807\u6570\u636e\u5e93
\nDROP DATABASE IF EXISTS test_db; — \u5220\u9664\u6570\u636e\u5e93<\/p>\n
— 2. \u8868\u64cd\u4f5c（\u4ee5\u5b66\u751f\u8868\u4e3a\u4f8b）
\nCREATE TABLE IF NOT EXISTS student (
\n id INT PRIMARY KEY AUTO_INCREMENT, — \u4e3b\u952e+\u81ea\u589e
\n name VARCHAR(50) NOT NULL, — \u59d3\u540d（\u975e\u7a7a）
\n age INT, — \u5e74\u9f84
\n gender VARCHAR(10), — \u6027\u522b
\n score DECIMAL(5,2), — \u5206\u6570（5\u4f4d\u6570\u5b57，2\u4f4d\u5c0f\u6570）
\n create_time DATETIME DEFAULT CURRENT_TIMESTAMP — \u521b\u5efa\u65f6\u95f4（\u9ed8\u8ba4\u5f53\u524d\u65f6\u95f4）
\n);<\/p>\n
— \u67e5\u770b\u8868\u7ed3\u6784
\nDESC student;<\/p>\n
— \u4fee\u6539\u8868（\u6dfb\u52a0\u5b57\u6bb5）
\nALTER TABLE student ADD COLUMN class VARCHAR(20);<\/p>\n
— \u5220\u9664\u8868
\nDROP TABLE IF EXISTS student;<\/p>\n
— 1. \u65b0\u589e\u6570\u636e（INSERT）
\n— \u65b9\u5f0f1：\u6307\u5b9a\u5b57\u6bb5
\nINSERT INTO student (name, age, gender, score, class)
\nVALUES ('\u5f20\u4e09', 18, '\u7537', 90.5, '\u9ad8\u4e00(1)\u73ed');<\/p>\n
— \u65b9\u5f0f2：\u6279\u91cf\u65b0\u589e
\nINSERT INTO student (name, age, gender, score, class)
\nVALUES
\n('\u674e\u56db', 17, '\u5973', 88.0, '\u9ad8\u4e00(1)\u73ed'),
\n('\u738b\u4e94', 18, '\u7537', 95.5, '\u9ad8\u4e00(2)\u73ed');<\/p>\n
— 2. \u4fee\u6539\u6570\u636e（UPDATE）：\u5fc5\u987b\u52a0WHERE，\u5426\u5219\u4fee\u6539\u5168\u8868！
\nUPDATE student
\nSET score = 92.0, class = '\u9ad8\u4e00(1)\u73ed'
\nWHERE id = 2;<\/p>\n
— 3. \u5220\u9664\u6570\u636e（DELETE）：\u5fc5\u987b\u52a0WHERE，\u5426\u5219\u5220\u9664\u5168\u8868！
\nDELETE FROM student WHERE id = 3;<\/p>\n
— \u6e05\u7a7a\u8868（\u81ea\u589e\u4e3b\u952e\u91cd\u7f6e）
\nTRUNCATE TABLE student;<\/p>\n
\u67e5\u8be2\u662f SQL \u6700\u5e38\u7528\u7684\u529f\u80fd，\u4ece\u7b80\u5355\u5230\u590d\u6742\u9010\u6b65\u638c\u63e1：<\/p>\n
— \u67e5\u8be2\u6240\u6709\u5b57\u6bb5（*）：\u751f\u4ea7\u73af\u5883\u5c3d\u91cf\u907f\u514d，\u6307\u5b9a\u5b57\u6bb5\u66f4\u9ad8\u6548
\nSELECT * FROM student;<\/p>\n
— \u67e5\u8be2\u6307\u5b9a\u5b57\u6bb5
\nSELECT name, age, score FROM student;<\/p>\n
— \u53bb\u91cd\u67e5\u8be2（DISTINCT）
\nSELECT DISTINCT class FROM student;<\/p>\n
— \u522b\u540d（AS）：\u7b80\u5316\u5b57\u6bb5\/\u8868\u540d
\nSELECT name AS \u59d3\u540d, age AS \u5e74\u9f84, score AS \u5206\u6570 FROM student AS s;<\/p>\n
— \u57fa\u672c\u6761\u4ef6：=\u3001>\u3001<\u3001>=\u3001<=\u3001!=\/<>
\nSELECT * FROM student WHERE score >= 90;<\/p>\n
— \u591a\u6761\u4ef6：AND（\u4e14）\u3001OR（\u6216）\u3001NOT（\u975e）
\nSELECT * FROM student WHERE age > 17 AND gender = '\u5973';<\/p>\n
— \u8303\u56f4\u67e5\u8be2：BETWEEN…AND…
\nSELECT * FROM student WHERE score BETWEEN 85 AND 95;<\/p>\n
— \u6a21\u7cca\u67e5\u8be2：LIKE（%\u4efb\u610f\u5b57\u7b26，_\u5355\u4e2a\u5b57\u7b26）
\nSELECT * FROM student WHERE name LIKE '\u5f20%'; — \u59d3\u5f20\u7684\u6240\u6709\u540d\u5b57
\nSELECT * FROM student WHERE name LIKE '\u5f20_'; — \u59d3\u5f20\u4e14\u540d\u5b572\u4e2a\u5b57<\/p>\n
— \u7a7a\u503c\u5224\u65ad：IS NULL \/ IS NOT NULL
\nSELECT * FROM student WHERE age IS NOT NULL;<\/p>\n
— \u679a\u4e3e\u67e5\u8be2：IN
\nSELECT * FROM student WHERE class IN ('\u9ad8\u4e00(1)\u73ed', '\u9ad8\u4e00(2)\u73ed');<\/p>\n
— \u5347\u5e8f（ASC，\u9ed8\u8ba4）\u3001\u964d\u5e8f（DESC）
\nSELECT * FROM student ORDER BY score DESC, age ASC;<\/p>\n
\u7528\u4e8e\u7edf\u8ba1\u6570\u636e，\u5e38\u7528：COUNT（\u8ba1\u6570）\u3001SUM（\u6c42\u548c）\u3001AVG（\u5e73\u5747）\u3001MAX（\u6700\u5927）\u3001MIN（\u6700\u5c0f）<\/p>\n
— \u7edf\u8ba1\u603b\u4eba\u6570
\nSELECT COUNT(*) AS \u603b\u4eba\u6570 FROM student;<\/p>\n
— \u7edf\u8ba1\u7537\u751f\u4eba\u6570（COUNT\u6307\u5b9a\u5b57\u6bb5\u907f\u514dNULL）
\nSELECT COUNT(id) AS \u7537\u751f\u4eba\u6570 FROM student WHERE gender = '\u7537';<\/p>\n
— \u5e73\u5747\u5206\u3001\u603b\u5206\u3001\u6700\u9ad8\u5206
\nSELECT
\n AVG(score) AS \u5e73\u5747\u5206,
\n SUM(score) AS \u603b\u5206,
\n MAX(score) AS \u6700\u9ad8\u5206
\nFROM student;<\/p>\n
\u7ed3\u5408\u805a\u5408\u51fd\u6570，\u6309\u6307\u5b9a\u5b57\u6bb5\u5206\u7ec4\u7edf\u8ba1：<\/p>\n
— \u6309\u73ed\u7ea7\u5206\u7ec4，\u7edf\u8ba1\u6bcf\u4e2a\u73ed\u7684\u4eba\u6570\u3001\u5e73\u5747\u5206
\nSELECT
\n class AS \u73ed\u7ea7,
\n COUNT(*) AS \u4eba\u6570,
\n AVG(score) AS \u5e73\u5747\u5206
\nFROM student
\nGROUP BY class;<\/p>\n
— \u5206\u7ec4\u540e\u7b5b\u9009：HAVING（\u533a\u522b\u4e8eWHERE：WHERE\u7b5b\u9009\u884c，HAVING\u7b5b\u9009\u5206\u7ec4）
\nSELECT
\n class AS \u73ed\u7ea7,
\n COUNT(*) AS \u4eba\u6570
\nFROM student
\nGROUP BY class
\nHAVING COUNT(*) > 5; — \u7b5b\u9009\u4eba\u6570\u5927\u4e8e5\u7684\u73ed\u7ea7<\/p>\n
\u4e0d\u540c\u6570\u636e\u5e93\u8bed\u6cd5\u7565\u6709\u5dee\u5f02，\u65b0\u624b\u91cd\u70b9\u638c\u63e1 MySQL：<\/p>\n
— MySQL：LIMIT \u8d77\u59cb\u4f4d\u7f6e（\u4ece0\u5f00\u59cb）, \u6761\u6570
\nSELECT * FROM student LIMIT 0, 10; — \u7b2c1\u9875，\u6bcf\u987510\u6761
\nSELECT * FROM student LIMIT 10, 10; — \u7b2c2\u9875，\u6bcf\u987510\u6761<\/p>\n
— SQL Server：TOP \/ OFFSET…FETCH
\nSELECT TOP 10 * FROM student;<\/p>\n
— Oracle：ROWNUM
\nSELECT * FROM (SELECT *, ROWNUM rn FROM student) WHERE rn BETWEEN 1 AND 10;<\/p>\n
\u5f53\u6570\u636e\u5206\u5e03\u5728\u591a\u5f20\u8868\u65f6（\u5982\u5b66\u751f\u8868 + \u6210\u7ee9\u8868 + \u8bfe\u7a0b\u8868），\u9700\u8981\u8fde\u63a5\u67e5\u8be2：<\/p>\n
\u5148\u521b\u5efa\u5173\u8054\u8868\u793a\u4f8b：<\/p>\n
— \u8bfe\u7a0b\u8868
\nCREATE TABLE course (
\n cid INT PRIMARY KEY AUTO_INCREMENT,
\n cname VARCHAR(50) NOT NULL — \u8bfe\u7a0b\u540d
\n);<\/p>\n
— \u6210\u7ee9\u8868（\u5173\u8054\u5b66\u751f\u548c\u8bfe\u7a0b）
\nCREATE TABLE score (
\n sid INT, — \u5173\u8054student.id
\n cid INT, — \u5173\u8054course.cid
\n score DECIMAL(5,2),
\n PRIMARY KEY (sid, cid), — \u590d\u5408\u4e3b\u952e
\n FOREIGN KEY (sid) REFERENCES student(id), — \u5916\u952e\u7ea6\u675f
\n FOREIGN KEY (cid) REFERENCES course(cid)
\n);<\/p>\n
— \u5185\u8fde\u63a5（INNER JOIN）：\u53ea\u8fd4\u56de\u4e24\u8868\u5339\u914d\u7684\u6570\u636e
\nSELECT
\n s.name AS \u5b66\u751f\u59d3\u540d,
\n c.cname AS \u8bfe\u7a0b\u540d,
\n sc.score AS \u5206\u6570
\nFROM student s
\nINNER JOIN score sc ON s.id = sc.sid
\nINNER JOIN course c ON sc.cid = c.cid;<\/p>\n
— \u5de6\u8fde\u63a5（LEFT JOIN）：\u8fd4\u56de\u5de6\u8868\u6240\u6709\u6570\u636e，\u53f3\u8868\u65e0\u5339\u914d\u5219\u4e3aNULL
\nSELECT
\n s.name AS \u5b66\u751f\u59d3\u540d,
\n c.cname AS \u8bfe\u7a0b\u540d,
\n sc.score AS \u5206\u6570
\nFROM student s
\nLEFT JOIN score sc ON s.id = sc.sid
\nLEFT JOIN course c ON sc.cid = c.cid;<\/p>\n
— \u53f3\u8fde\u63a5（RIGHT JOIN）：\u8fd4\u56de\u53f3\u8868\u6240\u6709\u6570\u636e，\u5de6\u8868\u65e0\u5339\u914d\u5219\u4e3aNULL
\n— \u5168\u8fde\u63a5（FULL JOIN）：\u8fd4\u56de\u4e24\u8868\u6240\u6709\u6570\u636e（MySQL\u4e0d\u652f\u6301，\u9700\u7528UNION\u6a21\u62df）<\/p>\n
\u5c06\u4e00\u4e2a\u67e5\u8be2\u7ed3\u679c\u4f5c\u4e3a\u53e6\u4e00\u4e2a\u67e5\u8be2\u7684\u6761\u4ef6 \/ \u6570\u636e\u6e90，\u5206\u4e3a：<\/p>\n
— \u6807\u91cf\u5b50\u67e5\u8be2：\u67e5\u8be2\u5206\u6570\u9ad8\u4e8e\u5e73\u5747\u5206\u7684\u5b66\u751f
\nSELECT name, score FROM student
\nWHERE score > (SELECT AVG(score) FROM student);<\/p>\n
— \u5217\u5b50\u67e5\u8be2：\u67e5\u8be2\u9ad8\u4e00(1)\u73ed\u7684\u6240\u6709\u5b66\u751f\u6210\u7ee9
\nSELECT * FROM score
\nWHERE sid IN (SELECT id FROM student WHERE class = '\u9ad8\u4e00(1)\u73ed');<\/p>\n
— \u8868\u5b50\u67e5\u8be2：\u5c06\u5b50\u67e5\u8be2\u7ed3\u679c\u4f5c\u4e3a\u4e34\u65f6\u8868
\nSELECT t.name, t.\u5e73\u5747\u5206
\nFROM (
\n SELECT class, AVG(score) AS \u5e73\u5747\u5206 FROM student GROUP BY class
\n) t
\nWHERE t.\u5e73\u5747\u5206 > 90;<\/p>\n
— \u7ed9\u5206\u6570\u5206\u7ea7
\nSELECT
\n name,
\n score,
\n CASE
\n WHEN score >= 90 THEN '\u4f18\u79c0'
\n WHEN score >= 80 THEN '\u826f\u597d'
\n WHEN score >= 60 THEN '\u53ca\u683c'
\n ELSE '\u4e0d\u53ca\u683c'
\n END AS \u7b49\u7ea7
\nFROM student;<\/p>\n
\u4fdd\u8bc1\u591a\u6b65\u64cd\u4f5c\u8981\u4e48\u5168\u6210\u529f，\u8981\u4e48\u5168\u5931\u8d25（\u5982\u8f6c\u8d26）：<\/p>\n
START TRANSACTION; — \u5f00\u542f\u4e8b\u52a1
\nUPDATE account SET balance = balance – 100 WHERE id = 1;
\nUPDATE account SET balance = balance + 100 WHERE id = 2;
\nCOMMIT; — \u63d0\u4ea4\u4e8b\u52a1（\u751f\u6548）
\n— ROLLBACK; — \u56de\u6eda（\u51fa\u9519\u65f6\u64a4\u9500\u64cd\u4f5c）<\/p>\n
\u63d0\u5347\u67e5\u8be2\u6548\u7387，\u65b0\u624b\u91cd\u70b9\u638c\u63e1\u521b\u5efa\u8bed\u6cd5：<\/p>\n
— \u521b\u5efa\u7d22\u5f15（\u9488\u5bf9\u67e5\u8be2\u9891\u7e41\u7684\u5b57\u6bb5）
\nCREATE INDEX idx_student_name ON student(name);<\/p>\n
— \u67e5\u770b\u7d22\u5f15
\nSHOW INDEX FROM student;<\/p>\n
— \u5220\u9664\u7d22\u5f15
\nDROP INDEX idx_student_name ON student;<\/p>\n
SQL\u8bed\u53e5\u7684\u7cbe\u901a\u9700\u8981\u8fdb\u884c\u5927\u91cf\u7684\u7ec3\u4e60，\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5b66\u4e60\u7684\u5efa\u8bae\u548c\u63a8\u8350\u7ec3\u4e60\u7684\u5e73\u53f0\u3002<\/p>\n
\u63a8\u8350\u65b0\u624b\u901a\u8fc7\u4ee5\u4e0b\u65b9\u5f0f\u5de9\u56fa：<\/p>\n
\u76ee\u5f55
\n1. \u4ec0\u4e48\u662f SQL
\n2. \u73af\u5883\u51c6\u5907（\u65b0\u624b\u63a8\u8350）
\n\u4e8c\u3001SQL \u5165\u95e8：\u6838\u5fc3\u8bed\u6cd5（CRUD）
\n1. \u6570\u636e\u5e93\u4e0e\u8868\u64cd\u4f5c（DDL）
\n2. \u6570\u636e\u64cd\u4f5c（DML）：\u589e\u5220\u6539
\n3. \u6570\u636e\u67e5\u8be2（DQL）：\u6700\u6838\u5fc3\u7684 SELECT
\n（1）\u57fa\u7840\u67e5\u8be2
\n（2<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[768,100],"topic":[],"class_list":["post-76031","post","type-post","status-publish","format-standard","hentry","category-server","tag-sql","tag-100"],"yoast_head":"\n