mysql - #1067 - Invalid default value

mysql 中无法设置默认值为函数或者表达式，如果你强制设置时，就会报错误：#1067 - Invalid default value。

这不是mysql的bug，而是故意这么设计的。参看：

http://dev.mysql.com/doc/refman/5.0/en/data-type-defaults.html

这里写道：

"The DEFAULT value clause in a data type specification indicates a default value for a
column. With one exception, the default value must be a constant; it cannot be a function
or an expression. This means, for example, that you cannot set the default for a date
column to be the value of a function such as NOW() or CURRENT_DATE."

简单来说就是默认值不能是函数和表达式，所有才有上面的错误信息。

下面是一个例子，不使用函数和表达式的默认值：

来自： http://stackoverflow.com/questions/168736/how-do-you-set-a-default-value-for-a-mysql-datetime-column

mysql> create table test (str varchar(32), ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP);

Query OK, 0 rows affected (0.00 sec)

mysql> desc test;

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

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

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

| str | varchar(32) | YES | | NULL | |

| ts | timestamp | NO | | CURRENT_TIMESTAMP | |

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

2 rows in set (0.00 sec)

mysql> insert into test (str) values ("demo");

Query OK, 1 row affected (0.00 sec)

mysql> select * from test;

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

| str | ts |

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

| demo | 2008-10-03 22:59:52 |

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

1 row in set (0.00 sec)

mysql>

参考资料：

Date and Time Function
http://dev.mysql.com/doc/refman/5.0/en/date-and-time-functions.html