Re: Creative use of CASE in a GROUP BY clause

On Mon, 18 Mar 2002 13:14:46
"Dorian Taylor" <leg0(at)hotmail(dot)com> wrote:

> I'm trying to figure out how to craft a query that I can embed into a piece
> of code that can be passed a bind value in order to dictate how it should
> behave on GROUP BY, sparing me from having to write separate queries for N
> functions and/or columns I may want to group my query by.
>
> e.g. SELECT COUNT(foo) FROM bar GROUP BY CASE (? IS NOT NULL) THEN thiscol
> ELSE thatcol END
>
> If thiscol and thatcol aren't the same type, the CASE bombs out. I suppose

If so, you may need to cast one of them.

e.g.
SELECT COUNT(foo) FROM bar
GROUP BY CASE WHEN (? IS NOT NULL)
THEN thiscol::TEXT
ELSE thatcol -- if the type of thatcol is TEXT
END;

> ultimately it would be a matter of reducing each column definition in the
> CASE to a boolean expression, but I'm not sure what that would syntactically
> look like, as simply declaring a column in GROUP BY is obviously shorthand
> for something.
>

Regards,
Masaru Sugawara