| From: | Stephan Szabo <sszabo(at)megazone23(dot)bigpanda(dot)com> |
|---|---|
| To: | Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Zeugswetter Andreas SB SD <ZeugswetterA(at)spardat(dot)at>, Peter Eisentraut <peter_e(at)gmx(dot)net>, Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: SET NULL / SET NOT NULL |
| Date: | 2002-03-26 05:59:06 |
| Message-ID: | 20020325214602.E47891-100000@megazone23.bigpanda.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Tue, 26 Mar 2002, Christopher Kings-Lynne wrote:
> > Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au> writes:
> > > I have throught of at least two problems with changing nullability. The
> > > first is primary keys. I have to prevent people setting a
> > column involved
> > > in a PK to null, right?
> >
> > Probably so.
>
> And foreign keys - foreign keys only have to reference UNIQUE, right? The
> nullability isn't an issue?
That should be fine.
> Lastly - in a multicolumn primary key, does EVERY column in the key need to
> be NOT NULL?
Well, it looks like the primary key will not be satisfied if any of the
values are NULL.
In my SQL 92 draft, 11.7 Syntax Rules 3a says:
If the <unique specification> specifies PRIMARY KEY, then let
SC be the <search condition>:
UNIQUE ( SELECT UCL FROM TN )
AND
( UCL ) IS NOT NULL
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