MySQLtruncatetable语句• 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)
truncated 带where
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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