| From: | Doug McNaught <doug(at)mcnaught(dot)org> |
|---|---|
| To: | "alex b(dot)" <mailinglists1(at)gmx(dot)de> |
| Cc: | Postgresql General <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: odd error... |
| Date: | 2003-05-10 22:11:53 |
| Message-ID: | m3u1c2jvti.fsf@varsoon.wireboard.com |
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| Lists: | pgsql-general |
"alex b." <mailinglists1(at)gmx(dot)de> writes:
> > Column "mp3checksum" of table "tcontent" needs a UNIQUE
> > constraint--does it have one?
>
> no it doesn't - because it is possible that the same exact file might
> be existent on multiple CDs...
> and therefore "mp3checksum" cannot have a UNIQUE constraint.
> am I right?
Then "mp3checksum" can't be a foreign key--a foreign key must be
unique in its own table. If "tcontent" has a primary key, use that as
the foreign key in in the other table; if it doesn't, you might want
to create a SERIAL column to serve as the primary key.
-Doug
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