# [EMAIL PROTECTED] / 2003-06-25 12:05:49 +0800:
> //Wrong sql statement
> alter table p_asset add mydate datetime default now();
> alter table p_asset add mydate datetime default time();
> alter table p_asset add mydate datetime default now;
> alter table p_asset add mydate datetime default time;
> alter table p_asset add mydate datetime default date();
> alter table p_asset add mydate datetime default datetime();
>
>
> How can I add the default now value into the specified column?
> I try to find in the mysql manual,but in the default value
> charter,no relative information can be found.
There *is* relevant information in the manual:
http://www.mysql.com/doc/en/CREATE_TABLE.html:
A DEFAULT value has to be a constant, it cannot be a function or an
expression.
http://www.mysql.com/doc/en/DATETIME.html:
The TIMESTAMP column type provides a type that you can use to
automatically mark INSERT or UPDATE operations with the current date
and time. If you have multiple TIMESTAMP columns, only the first one
is updated automatically.
Automatic updating of the first TIMESTAMP column occurs under any of
the following conditions:
* The column is not specified explicitly in an INSERT or LOAD
DATA INFILE statement.
* The column is not specified explicitly in an UPDATE statement
and some other column changes value. (Note that an UPDATE that
sets a column to the value it already has will not cause the
TIMESTAMP column to be updated, because if you set a column to
its current value, MySQL ignores the update for efficiency.)
* You explicitly set the TIMESTAMP column to NULL.
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