From: | hubert depesz lubaczewski <depesz(at)depesz(dot)com> |
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To: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
Cc: | Mai Peng <maily(dot)peng(at)webedia-group(dot)com>, Pgsql-admin <pgsql-admin(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Design database |
Date: | 2021-02-03 16:44:59 |
Message-ID: | 20210203164459.GA17357@depesz.com |
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Lists: | pgsql-admin |
On Wed, Feb 03, 2021 at 08:35:41AM -0700, David G. Johnston wrote:
> On Wed, Feb 3, 2021 at 8:23 AM Mai Peng <[1]maily(dot)peng(at)webedia-group(dot)com> wrote:
>
> Hello,
>
> I’ve got a table name publication, and another table named publication_item.
> Each publication_item is linked to a publication by publication_id.
> How could I add a constraint that check each publication has one or more publication_item when a tuple is inserted ?
> I don’t want to store items in the same table as publication because we could have 1-> n items.
>
> [2]https://www.postgresql.org/docs/current/tutorial-fk.html
I don't think it helps. Fkey can check that publication_item contains
valid publication_id, but doesn't ensure that every publication has at
least one item.
As for the problem of OP, I think this describes working solution:
https://www.depesz.com/2017/07/03/how-to-make-sure-there-is-always-at-least-one-sub-record/
Best regards,
depesz
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