On Wed, Jul 7, 2010 at 8:48 AM, Johan Andersson <warb@xxxxxxxx> wrote:
It isn't very clear just what modification it is you're tracking, a specific column or the entire row?
Is this a column of type timestamp?
You can do a comparison between OLD.XXX and NEW.XXX in a before-update trigger but you will need to take into account null values. For example, is it possible for the modified flag go from non-null to null, and if so what does that mean?
Suppose the update statement explicitly sets XXX to the same value it already has, is that updating it or not?
Hello!
I am trying to write a trigger for updating a modification column and am
having some trouble getting it to behave as I want.
The trigger should set the column to the supplied value if it is set in the
UPDATE statement and to the current timestamp [NOW()] if it is not. The
problem is that I don't know how to check if the column is set or not. I can
check the column's value for NULL but that doesn't work if I want the column
to accept NULL values (meaning "unmodified").
It isn't very clear just what modification it is you're tracking, a specific column or the entire row?
Is this a column of type timestamp?
You can do a comparison between OLD.XXX and NEW.XXX in a before-update trigger but you will need to take into account null values. For example, is it possible for the modified flag go from non-null to null, and if so what does that mean?
Suppose the update statement explicitly sets XXX to the same value it already has, is that updating it or not?
