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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

DELETE FROM tbl_name [[AS] tbl_alias]
    [WHERE where_condition]
    [ORDER BY ...]
    [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
CREATE TABLE t1 (a bigint(3), b bigint(5) primary key);
insert INTO t1 VALUES (1,1),(1,2);
delete from t1 where a=1 limit 1;

mysql> select * from t1;
+------+------+
| a    | b    |
+------+------+
|    1 |    2 |
+------+------+
  • 多表示例：

同时也支持多表 JOIN 语句。

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

mysql> select * from t1;
+------+
| a    |
+------+
|    1 |
|    4 |
+------+
2 rows in set (0.00 sec)

drop database if exists db1;
drop database if exists db2;
create database db1;
create database db2;
use db2;
drop table if exists t1;
create table t1 (a int);
insert into t1 values (1),(2),(4);
use db1;
drop table if exists t2;
create table t2 (b int);
insert into t2 values(1),(2),(3);
delete from db1.t2, db2.t1 using db1.t2 join db2.t1 on db1.t2.b = db2.t1.a where 2 > 1;

mysql> select * from db1.t2;
+------+
| b    |
+------+
|    3 |
+------+
mysql> select * from db2.t1;
+------+
| a    |
+------+
|    4 |
+------+
1 row in set (0.00 sec)