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;