Re: Do I need a PK on a join table?

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Wed, 15 Feb 2006 15:06:58 GMT
Message-ID: <msHIf.30319$VV4.312654@ursa-nb00s0.nbnet.nb.ca>

Knut Stolze wrote:

> Bob Badour wrote:

>>Knut Stolze wrote:
 >>
>>In DB2, a primary key mixes two logical constraints (candidate key,
>>uniqueness) with a physical structure (index).

>
> No, not really. Granted, DB2 creates a unique index to support the primary
> key/unique constraint.

In other words, not really but, yes, exactly.

>>In DB2, uniqueness and candidate key are two logical constraints instead
>>of one due to the abominable NULL.

>
> With "uniqueness" your are referring to unique indexes not unique
> constraints, right?

Uniqueness is a logical constraint. Why one earth would you assume I refer to a physical structure??? I thought you said you understood basic knowledge.

>>>>If you have a strong argument for wanting no index, declare a uniqueness
>>>>constraint.
>>>
>>>Which will be enforced by a unique index...
>>
>>In that case, DB2 forces one to have an index when one has a strong
>>argument for not wanting it. That seems rather stupid to me.

>
> Sure. But how "strong" could such an argument possibly be?

By definition, strong enough to make forcing an index simply wrong. Would it help if I typed slower? Received on Wed Feb 15 2006 - 09:06:58 CST