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* Single row tables
@ 2005-01-11 14:45 KÖPFERL Robert <robert.koepferl@sonorys.at>
0 siblings, 1 reply; 4+ messages in thread
From: KÖPFERL Robert @ 2005-01-11 14:45 UTC (permalink / raw)
To: ; +Cc: pgsql-sql
Hi,
with what constraint or how can I ensure that one of my tables has exact one
record or 0..1 records?
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Single row tables
@ 2005-01-11 14:50 Dmitri Bichko <dbichko@genpathpharma.com>
0 siblings, 0 replies; 4+ messages in thread
From: Dmitri Bichko @ 2005-01-11 14:50 UTC (permalink / raw)
To: KÖPFERL Robert <robert.koepferl@sonorys.at>; +Cc: pgsql-sql
I suppose you could put a check constraint that forces a single value on a column with a unique index? Or an insert trigger that always inserts the same value into a unique field.
Out of curiosity, why do you need to do this?
Dmitri
-----Original Message-----
From: pgsql-sql-owner@postgresql.org [mailto:pgsql-sql-owner@postgresql.org] On Behalf Of KÖPFERL Robert
Sent: Tuesday, January 11, 2005 9:46 AM
Cc: pgsql-sql@postgresql.org
Subject: [SQL] Single row tables
Importance: High
Hi,
with what constraint or how can I ensure that one of my tables has exact one record or 0..1 records?
---------------------------(end of broadcast)---------------------------
TIP 7: don't forget to increase your free space map settings
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Single row tables
@ 2005-01-11 15:17 KÖPFERL Robert <robert.koepferl@sonorys.at>
0 siblings, 0 replies; 4+ messages in thread
From: KÖPFERL Robert @ 2005-01-11 15:17 UTC (permalink / raw)
To: ; +Cc: pgsql-sql
Also I thought of an UNIQUE constraint on a column with =const constraint.
But ....
It's for global configuration data that exists only once.
Making a key value thing was to weak typed for my taste.
> -----Original Message-----
> From: Dmitri Bichko [mailto:dbichko@genpathpharma.com]
> Sent: Dienstag, 11. Jänner 2005 15:50
> To: KÖPFERL Robert
> Cc: pgsql-sql@postgresql.org
> Subject: RE: [SQL] Single row tables
>
>
> I suppose you could put a check constraint that forces a
> single value on a column with a unique index? Or an insert
> trigger that always inserts the same value into a unique field.
>
> Out of curiosity, why do you need to do this?
>
> Dmitri
>
> -----Original Message-----
> From: pgsql-sql-owner@postgresql.org
> [mailto:pgsql-sql-owner@postgresql.org] On Behalf Of KÖPFERL Robert
> Sent: Tuesday, January 11, 2005 9:46 AM
> Cc: pgsql-sql@postgresql.org
> Subject: [SQL] Single row tables
> Importance: High
>
>
> Hi,
>
> with what constraint or how can I ensure that one of my
> tables has exact one record or 0..1 records?
>
> ---------------------------(end of
> broadcast)---------------------------
> TIP 7: don't forget to increase your free space map settings
>
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: Single row tables
@ 2005-01-12 06:39 sad <sad@bankir.ru>
parent: KÖPFERL Robert <robert.koepferl@sonorys.at>
0 siblings, 0 replies; 4+ messages in thread
From: sad @ 2005-01-12 06:39 UTC (permalink / raw)
To: KÖPFERL Robert <robert.koepferl@sonorys.at>; +Cc: pgsql-sql
On Tuesday 11 January 2005 17:45, KÖPFERL Robert wrote:
> Hi,
>
> with what constraint or how can I ensure that one of my tables has exact
> one record or 0..1 records?
A trigger procedure BEFORE INSERT would help you.
And a column type with only one possible field value would help you if you
define UNIQUE INDEX on a field of this (user-defined) type.
^ permalink raw reply [nested|flat] 4+ messages in thread
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2005-01-11 14:45 Single row tables KÖPFERL Robert <robert.koepferl@sonorys.at>
2005-01-12 06:39 ` sad <sad@bankir.ru>
2005-01-11 14:50 Re: Single row tables Dmitri Bichko <dbichko@genpathpharma.com>
2005-01-11 15:17 Re: Single row tables KÖPFERL Robert <robert.koepferl@sonorys.at>
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