Re: enforcing with unique indexes..

Try a rule or a triger that checks for 
NOT EXISTS ( select 1 from eyp_listing where group_id = New.group_id and
userid != New.userid) 



"Rajesh Kumar Mallah." wrote:
> 
> Hi ,
> 
> can anyone tell me how can i enforce below in a table.
> I want that no more that one distinct userid exists for a given group_id
> in the table.
> 
> 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.
> 
> SELECT  group_id  from eyp_listing group by group_id  having  count(distinct userid) > 1  ;
> 
> always returns empty.
> 
> can it be done with some sort of UNIQUE INDEX?
> 
> Regds
> MAllah.
> 
> --
> Rajesh Kumar Mallah,
> Project Manager (Development)
> Infocom Network Limited, New Delhi
> phone: +91(11)6152172 (221) (L) ,9811255597 (M)
> 
> Visit http://www.trade-india.com ,
> India's Leading B2B eMarketplace.
> 
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