MySQL版本区别5.5与5.7之DEFAULT CURRENT_TIMESTAMP

在5.5到5.6.4版本里，对于DEFAULT CURRENT_TIMESTAMP子句，只能TIMESTAMP类型列上指定。

而从5.6.5开始（也包括5.7），DEFAULT CURRENT_TIMESTAMP子句可以指定到TIMESTAMP或者DATETIME类型列上。

比如在5.5中：

mysql> select version();

+------------+

| version()  |

+------------+

| 5.5.48-log |

+------------+

1 row in set (0.00 sec)

mysql> use test;

Database changed

mysql> create table t1(id int, dt timestamp not null DEFAULT CURRENT_TIMESTAMP, dt1 datetime not null DEFAULT CURRENT_TIMESTAMP);

ERROR 1067 (42000): Invalid default value for 'dt1'

mysql>

而在5.7中：

mysql> select version();

+------------+

| version()  |

+------------+

| 5.7.11-log |

+------------+

1 row in set (0.00 sec)

mysql> use test;

Database changed

mysql> create table t1(id int, dt timestamp not null DEFAULT CURRENT_TIMESTAMP, dt1 datetime not null DEFAULT CURRENT_TIMESTAMP);

ERROR 1050 (42S01): Table 't1' already exists

mysql> drop table t1;

Query OK, 0 rows affected (0.38 sec)

mysql> create table t1(id int, dt timestamp not null DEFAULT CURRENT_TIMESTAMP, dt1 datetime not null DEFAULT CURRENT_TIMESTAMP);

Query OK, 0 rows affected (0.32 sec)

mysql> desc t1;

+-------+-----------+------+-----+-------------------+-------+

| Field | Type      | Null | Key | Default           | Extra |

+-------+-----------+------+-----+-------------------+-------+

| id    | int(11)   | YES  |     | NULL              |       |
| dt    | timestamp | NO   |     | CURRENT_TIMESTAMP |       |

| dt1   | datetime  | NO   |     | CURRENT_TIMESTAMP |       |

+-------+-----------+------+-----+-------------------+-------+

3 rows in set (0.10 sec)

mysql>