MySQL truncate table语句的使用
Truncate table语句用来删除/截断表里的所有数据
- 和delete删除所有表数据在逻辑上含义相同，但性能更快
- 类似执行了drop table和create table两个语句
mysql> select * from students_bak; +-----+----------+--------+---------+ | sid | sname | gender | dept_id | +-----+----------+--------+---------+ | 101 | zhangsan | male | 10 | | 1 | aa | 1 | 1 | +-----+----------+--------+---------+ 2 rows in set (0.00 sec) mysql> truncate table students_bak; Query OK, 0 rows affected (0.16 sec) mysql> select * from students_bak; Empty set (0.00 sec) mysql> set autocommit=off; Query OK, 0 rows affected (0.01 sec) mysql> select * from students3; +-----+-------+--------+---------+--------+ | sid | sname | gender | dept_id | sname2 | +-----+-------+--------+---------+--------+ | 100 | NULL | 1 | 1 | NULL | +-----+-------+--------+---------+--------+ 1 row in set (0.01 sec) mysql> truncate table students3; Query OK, 0 rows affected (0.06 sec) mysql> rollback; Query OK, 0 rows affected (0.00 sec) mysql> select * from students3; Empty set (0.00 sec) mysql> delete from students; Query OK, 5 rows affected (0.00 sec) mysql> select * from students; Empty set (0.00 sec) mysql> rollback; Query OK, 0 rows affected (0.07 sec) mysql> select * from students; +-----+-------+--------+---------+ | sid | sname | gender | dept_id | +-----+-------+--------+---------+ | 1 | aa | 3 | 1 | | 4 | cc | 3 | 1 | | 5 | dd | 1 | 2 | | 6 | aac | 1 | 1 | | 10 | a | 1 | 1 | +-----+-------+--------+---------+ 5 rows in set (0.00 sec)
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