Mr. Joerdens,
> I get no rows if the result column returned by the subselect
> contains NULL values. It works as expected if I remove the NULL values
> from the result set. Is this behaviour correct and if so, why?
I can see how that bug would happen. You may want to forward your
e-mail to pgsql-bugs.
Regardless, you'll find that you get faster results (as well as avoiding
the NULL bug) if you use the following form of the query:
SELECT name
FROM customer
WHERE NOT EXISTS (
SELECT customer_id
FROM salesorder
WHERE customer_id = customer.customer_id
);
Bruce, you may want to consider editing your next edition to include the
above modification. WHERE ... NOT IN is a bad idea for any subselect on
medium-large tables.
-Josh Berkus
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