On 2010-04-30, Lonni J Friedman <netllama@gmail.com> wrote:
> Greetings,
> I'm attempting to create a PL/PGSQL function with an IF/THEN
> conditional. Basically, all I really need is the ability to run a
> long/complex SQL query based on the value of the newest row of one
> column in a specific table (if its equal to 1 then run the SQL, if
> anything else don't run it). In pseudo code, something like:
>
> CREATE OR REPLACE FUNCTION foo0 RETURN text AS $$
> IF (SELECT current_status from table0 WHERE id in (SELECT max(id) FROM
> table0))='1' THEN
> <LONG SQL QUERY>
> END IF;
> LANGUAGE 'plpgsql' ;
>
>
> This seems like a fairly simple requirement, yet I can't find any way
> to do this without creating a function.
> The problem is that the
> long/complex SQL query needs to return multiple columns of output (not
> just a single value), and functions can only return a single
> value/column, so I'm a bit stuck on how to make this work.
>
> Is there an alternative solution that I'm missing?
functions can return multple columns.
or you could try this:
SELECT * FROM (
<long sql query>
) AS foo WHERE
((SELECT current_status from table0 WHERE id in (SELECT max(id) FROM table0))='1')
;
the planner should be is smart enough to see that the where clause is
independant to the from clause and immutable and so evaluate it once.
