Re: pgsql aggregate: conditional max

Weimao Ke wrote:
> Hi,
>
> I need a special aggregation function. For instance, given the
> following table data:
>
> aid | cat | weight
> ----------+---------+---------
> a1 | Drama | 1
> a1 | Romance | 6
> a1 | Short | 1
> a1 | Other | 7
> a2 | Comedy | 1
> a2 | Drama | 2
> a3 | Drama | 1
> a3 | Adult | 2
> a3 | Comedy | 1
> a3 | Other | 1
>
> I want to group by "aid" and choose the category (i.e., "cat") with
> the largest "weight":
>
> aid | max_weighted_cat
> ----+---------------------
> a1 | Other
> a2 | Drama
> a3 | Adult
>
> Any ideas? Thank you! :)
>

Should be able to do this with a standard max() aggregate.

select aid, cat, max(weight)
from table
group by aid, cat;

Jeff