dynamic sorting...

hi everybody.

i have a sp. i am passing two argument to it.
first one : _sort_column --> defines which column will be used in "order
by".
second : _sort_direction --> define sorting direction(asc or desc).

i writing sp as :

CREATE OR REPLACE FUNCTION ftest(_sort_column "varchar", _sort_direction
"varchar")
RETURNS refcursor AS
$BODY$
declare
_result_set refcursor;
begin
open _result_set for
select firstname, lastname from tb_test
order by
case
when _sort_column ilike 'lastname' then lastname
else firstname
end;
return _result_set;
end;$BODY$
LANGUAGE 'plpgsql';

this works fine, however the next doesnt(i couldnt compile it ) :
CREATE OR REPLACE FUNCTION ftest(_sort_column "varchar", _sort_direction
"varchar")
RETURNS refcursor AS
$BODY$
declare
_result_set refcursor;
begin
open _result_set for
select firstname, lastname from tb_test
order by
case
when _sort_column ilike 'lastname' then lastname
else firstname
end
case
when _sort_direction ilike 'asc' then asc
else desc
end;
return _result_set;
end;$BODY$
LANGUAGE 'plpgsql';

any suggestions to run it? (except EXECUTE SQLSTRING).

thanks a lot.

Yavuz Kavus wrote:
> this works fine, however the next doesnt(i couldnt compile it ) :
> CREATE OR REPLACE FUNCTION ftest(_sort_column "varchar", _sort_direction
> "varchar")
> RETURNS refcursor AS
> $BODY$
> declare
> _result_set refcursor;
> begin
> open _result_set for
> select firstname, lastname from tb_test
> order by
> case
> when _sort_column ilike 'lastname' then lastname
> else firstname
> end
> case
> when _sort_direction ilike 'asc' then asc
> else desc
> end;
> return _result_set;
> end;$BODY$
> LANGUAGE 'plpgsql';
>
> any suggestions to run it? (except EXECUTE SQLSTRING).
There isn't any other ;-)

The first example works, because you replaced something that
represents a _value_ by a case. But in the second example, you
replaces a _keyword_ by a case, and that won't work.

Even for the first example, using "execute ..." will probably be faster,
at least if tb_test has moderate size. Using "case" in the first example
is bound to confuse the optimizer, and leads potentially bad performance
IMHO.

greetings, Florian Pflug