Re: Query, view join question.

Hi Tom,

pgsql-general-owner(at)postgresql(dot)org schreef:
> "Joost Kraaijeveld" <J(dot)Kraaijeveld(at)Askesis(dot)nl> writes:
>> CREATE OR REPLACE VIEW even AS
>> SELECT DISTINCT abo_his.klantnummer,
> abo_his.artikelnummer, abo_his.code_retour,
> abo_klt.aantal_abonnementen, abo_klt.afgewerkt
>> FROM abo_his
>> JOIN abo_klt ON abo_his.klantnummer = abo_klt.klantnummer
>> WHERE abo_his.abonnement = 238
>> ORDER BY abo_his.klantnummer, abo_his.artikelnummer,
> abo_his.code_retour, abo_klt.aantal_abonnementen, abo_klt.afgewerkt;
>
> Okay ... but the view is constraining abo_his.abonnement and
> outputting abo_klt.aantal_abonnementen. Why would you assume that
> joining on klantnummer would cause these two fields to necessarily be
> the same?

In the table abo_klt there is no record where abo_klt.abonnement = 238 and abo_klt.afgewerkt > 0:

munt=# select * from abo_klt where abonnement = 238 and afgewerkt > 0;
...
(0 rows)

So I assumed that in no join between abo_his (which has no "afgewerkt" column at all ) and abo_klt (which has 0 records with a "afgewerkt" columns > 0) as created above ( with WHERE abo_his.abonnement = 238) there could be a record with both abonnement = 238 and afgewerk >0.

But there are:

on the view there are :
munt=# select * from even where afgewerkt > 0;
.....
(797 rows)

SO I must understand something wrong...

Groeten,

Joost Kraaijeveld
Askesis B.V.
Molukkenstraat 14
6524NB Nijmegen
tel: 024-3888063 / 06-51855277
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e-mail: J(dot)Kraaijeveld(at)Askesis(dot)nl
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