Re: function volatility

On Monday 22. November 2010 12.30.31 maps@navigator-info.com wrote:
>
> How to declare function that return set of data from tables? for
> example :
>
>
> CREATE TYPE "public"."cst_test" AS (
>   "code" VARCHAR(10),
>   "name" VARCHAR(50),
>   "quantity" NUMERIC(10,2) );
>
> CREATE OR REPLACE FUNCTION public."sf_test"(id_code VARCHAR)
>   RETURNS SETOF "public"."cst_test" AS
> $body$
> SELECT
>   t1.code,
>   t1.name,
>   t2.quantity
> FROM "public"."test_1" t1
>   INNER JOIN "public"."test_2" t2 ON t1.id_test1 = t2.id_test1
> WHERE t1.code = $1
> $body$
> LANGUAGE 'sql' ;
>
>
> It's STABLE, IMMUTABLE OR VOLATILE?
>

A function that modifies the database is VOLATILE.
A function that doesn't modify the database, but does database lookups,
is STABLE.
A function that doesn't modify the database, and doesn't do database
lookups (like SQRT(x)) is IMMUTABLE.

regards,
Leif B. Kristensen