Re: select

Knut P Lehre wrote:

> I have a table with fields:
> id      A       B       C       D       E       F
> where id is an int4 primary key.
> In this table there is information like:
> 1       a1      b1      xxx             xxx
> 2       a1      b1      xxx     xxx     xxx     xxx
> 3       a2      b2      xxx     xxx     xxx     xxx
> 4       a2      b2      xxx     xxx     xxx     xxx
> 5       a3      b3      xxx             xxx     xxx
> 6       a3      b3      xxx     xxx     xxx     xxx
> 7       a3      b3      xxx     xxx     xxx     xxx
> 8       a4      b4      xxx     xxx     xxx     xxx
> 9       a1      b1      xxx
> 10      a3      b3      xxx
> 11      a1      b3              xxx
> where xxx represents any information.
> My problem is: I only want to select one of the records which have the same
> combination of information in fields A and B, and that should be the record
> with the lowest id. Thus, the resultset should be:
> 1       a1      b1      xxx             xxx
> 3       a2      b2      xxx     xxx     xxx     xxx
> 5       a3      b3      xxx             xxx     xxx
> 8       a4      b4      xxx     xxx     xxx     xxx
> 11      a1      b3              xxx
> Importantly, I might not want the selected records listed in order of increasing
> id. They might be sorted according to the data in e.g. the C field.
>
> Suggestions/comments greatly appreciated.
>

Does this give you the result you are looking for?
SELECT * FROM (
SELECT DISTINCT ON (A,B) * FROM table ORDER BY id
) AS foo ORDER BY C ;

Regards, Christoph