DELETE

语法说明

DELETE 用于删除单表或多表中的记录。

语法结构

单表语法结构

1. DELETE FROM tbl_name [[AS] tbl_alias]
2. [WHERE where_condition]
3. [ORDER BY ...]
4. [LIMIT row_count]

DELETE 语句从 tbl_name 中删除行，并返回已删除的行数。

参数释义

  • WHERE 从句用于指定用于标识要删除哪些行的条件。若无 WHERE 从句，则删除所有行。
  • ORDER BY 从句，指按照指定的顺序删除行。
  • LIMIT 从句用于限制可删除的行数。

示例

  • 单表示例
1. CREATE TABLE t1 (a bigint(3), b bigint(5) primary key);
2. insert INTO t1 VALUES (1,1),(1,2);
3. delete from t1 where a=1 limit 1;

5. mysql> select * from t1;
6. +------+------+
7. | a    | b    |
8. +------+------+
9. |    1 |    2 |
10. +------+------+
  • 多表示例：

同时也支持多表 JOIN 语句。

1. drop table if exists t1;
2. drop table if exists t2;
3. create table t1 (a int);
4. insert into t1 values(1), (2), (4);
5. create table t2 (b int);
6. insert into t2 values(1), (2), (5);
7. delete t1 from t1 join t2 where t1.a = 2;

9. mysql> select * from t1;
10. +------+
11. | a    |
12. +------+
13. |    1 |
14. |    4 |
15. +------+
16. 2 rows in set (0.00 sec)

1. drop database if exists db1;
2. drop database if exists db2;
3. create database db1;
4. create database db2;
5. use db2;
6. drop table if exists t1;
7. create table t1 (a int);
8. insert into t1 values (1),(2),(4);
9. use db1;
10. drop table if exists t2;
11. create table t2 (b int);
12. insert into t2 values(1),(2),(3);
13. delete from db1.t2, db2.t1 using db1.t2 join db2.t1 on db1.t2.b = db2.t1.a where 2 > 1;

15. mysql> select * from db1.t2;
16. +------+
17. | b    |
18. +------+
19. |    3 |
20. +------+
21. mysql> select * from db2.t1;
22. +------+
23. | a    |
24. +------+
25. |    4 |
26. +------+
27. 1 row in set (0.00 sec)