PostgreSQL function returning multiple result sets

Question

Is it possible to return multiple result sets from a Postgres function, like in MSSQL:

CREATE PROCEDURE test

AS

SELECT * FROM first_table

SELECT * FROM se         


        

Answer 1

If first_table and second_table have the same layout, you can also just use

SELECT * FROM first_table WHERE ...
UNION ALL
SELECT * FROM second_table WHERE ...

[EDIT: Thanks to a commenter (whose name is probably not "null" :) ) for pointing out that UNION ALL is faster than UNION.]

Answer 2

A simpler way has been around since PostgreSQL 8.3:

CREATE FUNCTION test()
  RETURNS SETOF first_table AS
$func$
BEGIN

RETURN QUERY
SELECT * FROM first_table;

RETURN QUERY
SELECT * FROM second_table;   -- has to return same rowtype as first_table!

END
$func$ LANGUAGE plpgsql;

Call:

SELECT * FROM test();

Both result sets are appended to a single set returned from the function.
See the manual for RETURN QUERY.

Answer 3

Yes.

Example:

test=# create function x () returns setof integer language plpgsql as $$ begin return next 1; return next 2; end $$;
CREATE FUNCTION
test=# select * from x();
 x 
---
 1
 2
(2 rows)

You can of course use an existing table/view or a custom type for the returned type.

Example using language SQL:

test=# create table customer (name varchar, birth_date date);
CREATE TABLE
test=# create function y () returns setof customer language sql as $$ 
select * from customer
union all
select * from customer
$$;
CREATE FUNCTION
test=# insert into customer values ('joe', now()::date);
INSERT 0 1
test=# insert into customer values ('jill', now()::date);
INSERT 0 1
test=# select * from y();
 name | birth_date 
------+------------
 joe  | 2009-04-16
 jill | 2009-04-16
 joe  | 2009-04-16
 jill | 2009-04-16
(4 rows)

See here for doc

Answer 4

CREATE OR REPLACE FUNCTION "pr_GetCustomersAndOrders"()
RETURNS SETOF refcursor AS
$BODY$DECLARE
customerRC refcursor;
orderRC refcursor;
BEGIN
open customerRC FOR
SELECT * FROM customers;
RETURN NEXT customerRC;

open orderRC FOR
SELECT * FROM orders;
RETURN NEXT orderRC;
RETURN;
END;$BODY$
LANGUAGE 'plpgsql' VOLATILE;
ALTER FUNCTION "pr_GetCustomersAndOrders"() OWNER TO postgres;

I.o.w. using refcursors :)