MySQL 常用语法
MySQL 常用语法
数据库操作
创建数据库：
CREATE DATABASE database_name;
删除数据库：
DROP DATABASE database_name;
选择数据库：
USE database_name;
表操作
创建表：
CREATE TABLE table_name (column1 datatype constraints,column2 datatype constraints,...
);
删除表：
DROP TABLE table_name;
修改表结构：
ALTER TABLE table_name ADD column_name datatype;
ALTER TABLE table_name DROP COLUMN column_name;
ALTER TABLE table_name MODIFY COLUMN column_name datatype;
数据操作
插入数据：
INSERT INTO table_name (column1, column2, ...) VALUES (value1, value2, ...);
查询数据：
SELECT column1, column2, ... FROM table_name WHERE condition;
更新数据：
UPDATE table_name SET column1 = value1, column2 = value2 WHERE condition;
删除数据：
DELETE FROM table_name WHERE condition;
条件查询
WHERE 子句：
SELECT * FROM table_name WHERE column1 = value1 AND column2 > value2;
ORDER BY 排序：
SELECT * FROM table_name ORDER BY column1 ASC, column2 DESC;
LIMIT 限制结果数量：
SELECT * FROM table_name LIMIT 10;
GROUP BY 分组：
SELECT column1, COUNT(*) FROM table_name GROUP BY column1;
HAVING 分组条件：
SELECT column1, COUNT(*) FROM table_name GROUP BY column1 HAVING COUNT(*) > 1;
聚合函数
常用聚合函数：
SELECT COUNT(*) FROM table_name;
SELECT SUM(column1) FROM table_name;
SELECT AVG(column1) FROM table_name;
SELECT MAX(column1) FROM table_name;
SELECT MIN(column1) FROM table_name;
连接查询
内连接：
SELECT t1.column1, t2.column2 FROM table1 t1 INNER JOIN table2 t2 ON t1.id = t2.id;
左连接：
SELECT t1.column1, t2.column2 FROM table1 t1 LEFT JOIN table2 t2 ON t1.id = t2.id;
右连接：
SELECT t1.column1, t2.column2 FROM table1 t1 RIGHT JOIN table2 t2 ON t1.id = t2.id;
子查询
WHERE 子句中的子查询：
SELECT * FROM table1 WHERE column1 IN (SELECT column1 FROM table2 WHERE condition);
FROM 子句中的子查询：
SELECT * FROM (SELECT column1 FROM table1) AS temp_table;
索引操作
创建索引：
CREATE INDEX index_name ON table_name (column1, column2);
删除索引：
DROP INDEX index_name ON table_name;
事务控制
开启事务：
START TRANSACTION;
提交事务：
COMMIT;
回滚事务：
ROLLBACK;
用户权限
创建用户：
CREATE USER 'username'@'host' IDENTIFIED BY 'password';
授予权限：
GRANT ALL PRIVILEGES ON database_name.* TO 'username'@'host';
撤销权限：
REVOKE ALL PRIVILEGES ON database_name.* FROM 'username'@'host';
删除用户：
DROP USER 'username'@'host';
视图操作
创建视图：
CREATE VIEW view_name AS SELECT column1, column2 FROM table_name WHERE condition;
查询视图：
SELECT * FROM view_name;
删除视图：
DROP VIEW view_name;