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Date: Sat, 5 Oct 2002 15:13:12 +0100 (BST)
Subject: Re: enforcing with unique indexes..
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To: <mallah@trade-india.com>
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>
> ie i want 1 to 1 mapping between group_id and userid so that , there
> shud not be a  single group_id having more that one kind of userid.
>
> can it be done with some sort of UNIQUE INDEX?

If you want multiple groups but the user should always be the same

1  1  ok
1  1  ok
2  1  ok
3  2  ok
3  3  bad

Perhaps you should normalise a bit further with a separate group_user
table - you could restrict that to being unique on group then.

- Richard Huxton