Question

Is there any way, in MySQL, to dynamically generate a field value? For example a field that stamps the exact date and time that a row was inserted.

You could just get the interface to do it (i.e. PHP) but in a case where you have more than one handler it would be safer if I could get MySQL to do it independently.

Answer 1

The MySQL TIMESTAMP data type has a special default called CURRENT_TIMESTAMP that does this.

Read all about it:

http://dev.mysql.com/doc/refman/5.1/en/timestamp.html

EDIT:
For the more generic case, use a trigger. You can set the value on an insert using a BEFORE INSERT triggers, and likewise you can set the value on updates using a separate BEFORE UPDATE trigger:

http://dev.mysql.com/doc/refman/5.1/en/create-trigger.html