Re: [HACKERS] Group By, NULL values and inconsistent behaviour.

On Mon, 26 Jan 1998, Darren King wrote:

>> The following is Informix behavior:
>>
>> > select b,c,sum(a) from t1 group by b,c;
>> b c (sum)
>>
>> x 5
>> z 3
>>
>> 2 row(s) retrieved.
>
>Here is where postgres seems to differ. Seems postgres is missing
>an implicit sort so that the grouping is done properly.
>
>Postgres will return _three_ rows...
>
>b c (sum)
> x 3
> z 3
> x 2

I'm running the current cvs and it gives me this.

select b,c,sum(a) from t1 group by b,c;
b|c |sum
-+--+---
|x | 1
|x | 2
|z | 3
|x | 2
(4 rows)

>> > select b,c,sum(a) from t1 group by b,c order by c;
>> b c (sum)
>>
>> x 5
>> z 3
>>
>> 2 row(s) retrieved.
>
>Even with the order by, postgres still returns _three_ rows...
>
>b c (sum)
> x 3
> x 2
> z 3

select b,c,sum(a) from t1 group by b,c order by c;
b|c |sum
-+--+---
|x | 1
|x | 2
|x | 2
|z | 3
(4 rows)

>For now, ignore the patch I sent. Appears from Andreas demo that the
>current postgres code will follow the Informix style with regard to
>grouping columns with NULL values. Now that I really think about it,
>it does make more sense.

I think I saw the patch committed this morning...?

Mike
[ Michael J. Maravillo Philippines Online ]
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[ http://www.philonline.com/~mmj/ (632) 890-0204 ]