Re: Do I need a PK on a join table?
From: David Portas <REMOVE_BEFORE_REPLYING_dportas_at_acm.org>
Date: 16 Feb 2006 14:03:18 -0800
Message-ID: <1140127398.241067.123360_at_o13g2000cwo.googlegroups.com>
> Well, you have to use _some_ mechanism on the internal layer to support the
> logical constructs on the conceptual layer.
Date: 16 Feb 2006 14:03:18 -0800
Message-ID: <1140127398.241067.123360_at_o13g2000cwo.googlegroups.com>
Knut Stolze wrote:
>
> Well, you have to use _some_ mechanism on the internal layer to support the
> logical constructs on the conceptual layer.
Not always. Sometimes you don't want or need an index for every unique constraint. For example:
If the key is a superkey with a candidate key already defined
If check constraints prevent duplicates
You may still need the constraint to support a foreign key. You don't
need the index.
If constraints on views prevent duplicates
-- David PortasReceived on Thu Feb 16 2006 - 23:03:18 CET