Table Variable and Table-Valued Function equivalent in PostgreSQL - sql

Question

I need to create a function in PostgreSQL for the following :
Query multiple tables based on a business logic (all result sets return the same type of data)
Compile all result sets into one table and return that table
Is it possible to accomplish this without using the temp tables in PostgreSQL?
I currently do this in Microsoft SQL server using Table Variables, below is a sample function:
create FUNCTION test(#search_in nvarchar(500))
RETURNS #data_table TABLE
(
item_id int,
item_type nvarchar(1),
first_name nvarchar(100),
last_name nvarchar(100))
) AS
BEGIN
-- from first table
if charindex('search_in_authors', #search_in) > 0
insert into #data_table
select item_id, 'a', first_name, last_name
from authors
where first_name = 'james'
-- from second table
if charindex('search_in_editors', #search_in) > 0
insert into #data_table
select item_id, 'e', first_name, last_name
from editors
where first_name = 'james'
-- from third table
if charindex('search_in_publishers', #search_in) > 0
insert into #data_table
select item_id, 'p', first_name, last_name
from publishes
where first_name = 'james'
-- there could be more like these based on the business logic...
(...)
-- finally return the records compiled in #data_table
RETURN
END
Sample calls to the function:
select * from dbo.test('search_in_authors')
select * from dbo.test('search_in_authors, search_in_editors')
select * from dbo.test('search_in_authors, search_in_editors,search_in_publishers ')
Are there any options in PostgreSQL to achieve this other than using a temp table ?
Thanks,
San

Answer 1

You can use RETURN QUERY to add the result of various queries to the output.
CREATE OR REPLACE FUNCTION public.testf()
RETURNS TABLE(id INTEGER, name text)
STABLE
AS $$
DECLARE
BEGIN
RETURN QUERY select 1 as id, 'abc' as name;
RETURN QUERY select 2 as id, 'def' as name;
RETURN QUERY select 3 as id, 'xyz' as name;
-- Final return as set is now complete.
return;
END;
$$ LANGUAGE plpgsql;
select * from public.testf();
id | name
----+------
1 | abc
2 | def
3 | xyz
(3 rows)