column: on update update?

[Michael Monnerie <michael.monnerie@xxxxxxxxxxxxxxxx>]

Hi, I fear this is a beginners question but I'm no SQL guru and couldn't 
find it out of the documentation.

For SpamAssassin, I have a table "awl" (auto white list), and there 
should be one field "lastupdate". I added it like this:
ALTER TABLE awl add column lastupdate timestamp default now();

But I also need the "lastupdate" be updated every time a field in that 
row is updated, so a statement like this:

ALTER TABLE awl add column lastupdate2 timestamp default now() on update 
set now();

But it doesn't work. Do I need a trigger? If yes, what would be the 
format? I never did triggers.

mfg zmi
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