| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Vik Fearing <vik(dot)fearing(at)dalibo(dot)com> |
| Cc: | Gavin Flower <GavinFlower(at)archidevsys(dot)co(dot)nz>, David G Johnston <david(dot)g(dot)johnston(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: "RETURNING PRIMARY KEY" syntax extension |
| Date: | 2014-06-09 17:13:23 |
| Message-ID: | 20140609171323.GF8406@alap3.anarazel.de |
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| Thread: | |
| Lists: | pgsql-hackers |
On 2014-06-09 13:42:22 +0200, Vik Fearing wrote:
> On 06/09/2014 09:06 AM, Gavin Flower wrote:
> > From memory all unique keys can be considered 'candidate primary keys',
> > but only one can be designated 'the PRIMARY KEY'.
>
> Almost. Candidate keys are also NOT NULL.
The list actually is a bit longer. They also cannot be partial.
There's generally also the restriction that for some contexts - like
e.g. foreign keys - primary/candidate keys may not be deferrable..
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
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