Re: BUG #3729: Query doesn't return the right answer - Mailing list pgsql-bugs

Andrius Glozeckas wrote:

> I have a parent_type_id linking to group_type_id on the same table
> (group_type). I am trying to get the groups with certain parent_type_id (be
> it null or 17) and the number of their children in the same query:
>
> SELECT g1.*, COUNT(g2.*)
> FROM group_type g1 LEFT JOIN group_type g2 ON g1.group_type_id =
> g2.parent_type_id
> WHERE g1.parent_type_id = null
> GROUP BY g1.name, g1.type, g1.choice, g1.multiple, g1.self_ref,
> g1.group_type_id, g1.parent_type_id
>
> But this doesn't give me any results, although there are a few records with
> parent_type_id = null and one with 17.

This is not a bug.  The correct syntax for testing for NULL is "column
IS NULL".  Do not use "column = NULL".

--
Alvaro Herrera                               http://www.PlanetPostgreSQL.org/
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