Re: [BUGS] General Bug Report: GROUP BY with NULL not done properly(Oracle8& DB/2 do this completely different)

Bruce Momjian wrote:

> Looks like this is fixed in 6.5.
>
> test=> SELECT a,sum(b) FROM z GROUP BY a;
> a|sum
> -+---
> 1| 6
> | 4
> (2 rows)
>
> >
> > ============================================================================
> > POSTGRESQL BUG REPORT TEMPLATE
> > ============================================================================
> >
> >
> > Your name :
> > Your email address : secret(at)kearneydev(dot)com
> >
> > Category : runtime: back-end: SQL
> > Severity : non-critical
> >
> > Summary: GROUP BY with NULL not done properly(Oracle8 & DB/2 do this completely different)
> >
> > System Configuration
> > --------------------
> > Operating System : Linux 2.2.7 Redhat 5.2
> >
> > PostgreSQL version : 6.4.2
> >
> > Compiler used : 2.7.2.3
> >
> > Hardware:
> > ---------
> > Linux tau.kearneydev.com 2.2.7 #3 Thu Apr 29 10:10:41 EDT 1999 i686 unknown
> >
> > Versions of other tools:
> > ------------------------
> >
> >
> > --------------------------------------------------------------------------
> >
> > Problem Description:
> > --------------------
> > The appearance of NULL in a table where a GROUP BY clause is
> > used causes the behavior of returning 1 line for every NULL.
> > Both Oracle8 and DB/2 perform this as I would expect. IE
> > a,b
> > 1,1
> > 1,2
> > NULL,1
> > NULL,2
> >
> > SELECT a,sum(b) GROUP BY a returns on Postgres:
> > 1,3
> > NULL,1
> > NULL,2
> >
> > On Oracle8, DB/2, etc.:
> > 1,3
> > NULL,3
> >
> > Cut&paste from Oracle8:
> > SQL> select * from z;
> >
> > A B
> > --------- ---------
> > 1 1
> > 1 2
> > 5
> > 10
> >
> > SQL> select a,sum(b) from z group by a;
> >
> > A SUM(B)
> > --------- ---------
> > 1 3
> > 15
> >
> > SQL>
> >
> > --------------------------------------------------------------------------
> >
> > Test Case:
> > ----------
> > CREATE TABLE z(a int4,b int4);
> > INSERT INTO z values (1,2);
> > INSERT INTO z VALUES (1,1);
> > INSERT INTO z(b) VALUES (1);
> > INSERT INTO z(b) VALUES (2);
> > SELECT a,sum(b) FROM z GROUP BY a;
> >
> >
> > --------------------------------------------------------------------------
> >
> > Solution:
> > ---------
> > For whatever reason I've observed many times that NULL<>NULL
> > under PostgreSQL, I've had to include many clauses in my
> > SQL statements to make up for this, perhaps if this was
> > corrected it would function properly.
> >
> > --------------------------------------------------------------------------
> >
> >
> >
>
> --
> Bruce Momjian | http://www.op.net/~candle
> maillist(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
> + If your life is a hard drive, | 830 Blythe Avenue
> + Christ can be your backup. | Drexel Hill, Pennsylvania 19026

It works fine with 1 variable, try it with 2. 6.4.2 worked fine for 1, it's just when you
GROUP BY 2 variables that contain NULLs issues start appearing.(Another reason it looks like a
bug, not a feature :))

David Secret
MIS Director
Kearney Development Co., Inc.