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@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
If constraints on views prevent duplicates

You may still need the constraint to support a foreign key. You don't need the index.

--
David Portas

Received on Thu Feb 16 2006 - 16:03:18 CST