Hi. I'm using PostgreSQL 7.4.2 under Fedora Core 1.
I have two tables with a single varchar(32) column in each. I'm trying
to find all the rows from one table that don't exist in the other
table. The query that I am using is:
select u.user_name from users u where u.user_name not in (select
user_name from iasusers);
(Actually, I'm doing something a bit more complex but this illustrates
the problem.)
It always seems to return 0 rows. As a test, I inserted a row into
users that I knew wasn't in iasuses but it didn't make a difference.
If I remove the 'not', the query returns the rows that exist in both
tables.
If I replace the subselect with a list, it seems to work the way that
I'd expect, i.e. "not in ('vic', 'joe')" it shows all the rows from
users except for vic and joe.
Am I doing something wrong or is this a bug?
Thanks,
-Vic