MySQL truncate table語句的使用

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Truncate table語句用來刪除/截斷表裡的所有數據

  • 和delete刪除所有表數據在邏輯上含義相同，但性能更快
  • 類似執行瞭drop table和create table兩個語句
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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