Re: SQL Question

Julian Scarfe wrote:

> From: "Alex" <alex@meerkatsoft.com>
>
>> - How can i select only the newest record for each ProdId ?
>>
>> 100    | 2005-04-01
>> 200    | 2005-04-01
>>
>
> DISTINCT ON was made for this and on the similar tables I have
> performs rather more efficiently than using a subquery.
>
> select distinct on (ProdId) ProdId , LastUpdate
> from produpdate
> order by ProdId , LastUpdate desc;
>
>> - How can i select to retrieve the last 2 dates in record
>>
>> 100    | 2005-04-01 | 2005-03-01
>> 200    | 2005-04-01 | 2005-03-01
>
>
> To get the previous one, my first thought is something like:
>
> select distinct on (ProdId) ProdId , LastUpdate
> from produpdate p1
> where LastUpdate <> (
>    select max(LastUpdate ) from produpdate p2 where p2.ProdId = p1.ProdId
> )
> order by ProdId , LastUpdate desc ;
>
> but there may be a much more efficient way of getting the nth result
> in general.
>
> Julian Scarfe
>
>
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>
Thanks for the help. will give it a try.

Alex