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* Foreign key with check?
@ 2005-07-27 20:08 Jeff Boes <jeff@endpoint.com>
0 siblings, 1 reply; 2+ messages in thread
From: Jeff Boes @ 2005-07-27 20:08 UTC (permalink / raw)
To: pgsql-sql
Given a table like this:
create table primary (
a integer primary key,
b boolean
);
And another like this:
create table secondary (
a integer,
some_other_fields
);
I would like a foreign key constraint on the "secondary" table that
looks something like:
foreign key (a, true) references primary (a, b)
That is, a row in "secondary" is allowed to reference a row in "primary"
if and only if that referenced row has (b = true).
I think I have to do this with an additional trigger. Any other options?
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: Foreign key with check?
@ 2005-07-27 20:37 Bruno Wolff III <bruno@wolff.to>
parent: Jeff Boes <jeff@endpoint.com>
0 siblings, 0 replies; 2+ messages in thread
From: Bruno Wolff III @ 2005-07-27 20:37 UTC (permalink / raw)
To: Jeff Boes <jeff@endpoint.com>; +Cc: pgsql-sql
On Wed, Jul 27, 2005 at 16:08:19 -0400,
Jeff Boes <jeff@endpoint.com> wrote:
> Given a table like this:
>
> create table primary (
> a integer primary key,
> b boolean
> );
>
> And another like this:
>
> create table secondary (
> a integer,
> some_other_fields
> );
>
>
> I would like a foreign key constraint on the "secondary" table that
> looks something like:
>
> foreign key (a, true) references primary (a, b)
>
> That is, a row in "secondary" is allowed to reference a row in "primary"
> if and only if that referenced row has (b = true).
If what you are saying is that all entries in secondary need to reference
a row in primary and in addition the referenced row must have b true, then
you can do this fairly simply using a bit of extra space.
Add a row b to secondary with a constraint that b = true. Then make the
foreign key reference on both a and b.
^ permalink raw reply [nested|flat] 2+ messages in thread
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