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I use timestamp on MySQL 5.x (with PHP) to remember event times. During development I had to update the table with a query that changes something in all columns. The timestamp was then reset to current time.

How can I make timestamp change only on inserts and not on updates or replace?

A late answer for others who may Google this: if you use a TIMESTAMP when you do manuals edits in your database; or if you have multiple TIMESTAMP columns and do not want to touch all of them; the MySQL manual says to assign the column to itself. You explicitly set the column to its current value (ie. "updated_on = updated_on"), so that it is not changed by the UPDATE. – user58777 Nov 12, 2010 at 16:22

Here's all you need to know . In short, though, I think this should do it:

ALTER TABLE `mytable`
CHANGE `mydatefield` `mydatefield`
TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
                I may be missing something but my table is (and was) defined this way but still the dates changed. From mysql explain: 'pur_time', 'timestamp', 'NO', '', 'CURRENT_TIMESTAMP', ''
– Nir
                May 3, 2009 at 16:34
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