Omar Bettin wrote:
Hi,
I have to compare an OLD.Value with a NEW.Value on PostgreSQL 8.2.4
plpgsql trigger function:
IF OLD.Value <> NEW.Value THEN
...
but, if OLD.Value IS NULL and NOT NEW.Value IS NULL the previous IF does
not work and I have to use this method:
IF (OLD.Value <> NEW.Value) OR (OLD.Value IS NULL AND NOT NEW.Value IS
NULL) THEN
...
this works!
Is that normal ?
yeah that is expected behaviour - NULL does not equal NULL. In cases
like that you might wnat to use:
IF OLD.Value IS DISTINCT FROM NEW.Value THEN
which handles NULL in the way you seem to expect it.
also look at
http://www.postgresql.org/docs/current/static/functions-comparison.html
for more details on that topic.
Stefan
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