Re: GROUPing by expressions, and subSELECTs

Shane Wright <me@shanewright.co.uk> writes:
> SELECT
>   [fields],
>   [expression],
>   (SELECT * FROM table2 WHERE [expression]) AS mynewfield
> FROM
>   table
> GROUP BY
>   [expression]

> But, it gives this error:

> ERROR: Sub-SELECT uses un-GROUPed attribute [table].[field] from outer 
> query

Yeah, the code is not bright enough to figure out that this could be
considered legitimate.  But try this:

SELECT [fields], myexpr, (SELECT * FROM table2 WHERE ss.myexpr) AS mynewfield
FROM (SELECT [fields],         [expression] as myexpr  FROM table  GROUP BY myexpr) AS ss
        regards, tom lane