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Re: BUG #3729: Query doesn't return the right answer

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Andrius Glozeckas <ndrs(at)systemap(dot)com>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #3729: Query doesn't return the right answer
Date: 2007-11-08 14:49:28
Message-ID: 20071108144928.GG2938@alvh.no-ip.org (view raw or flat)
Thread:
Lists: 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/
"Changing the world ... one keyboard at a time!"
                         (www.DVzine.org)

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Subject: Re: BUG #3729: Query doesn't return the right answer
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Subject: Re: BUG #3716: utf8 crash with replace

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