sql - Return a query from a function?

Question

I am using PostgreSQL 8.4 and I want to create a function that returns a query with many rows.
The following function does not work:

create function get_names(varchar) returns setof record AS $$
declare
    tname alias for $1;
    res setof record;
begin
    select * into res from mytable where name = tname;
    return res;
end;
$$ LANGUAGE plpgsql;

The type record only allows single row.

How to return an entire query? I want to use functions as query templates.

Answer 1

CREATE OR REPLACE FUNCTION get_names(_tname varchar)
  RETURNS TABLE (col_a integer, col_b text) AS
$func$
BEGIN
   RETURN QUERY
   SELECT t.col_a, t.col_b  -- must match RETURNS TABLE
   FROM   mytable t
   WHERE  t.name = _tname;    
END
$func$  LANGUAGE plpgsql;

Call like this:

SELECT * FROM get_names('name')

Major points:

• Use RETURNS TABLE, so you don't have to provide a list of column names with every call.

• Use RETURN QUERY, much simpler.

• Table-qualify column names to avoid naming conflicts with identically named OUT parameters (including columns declared with RETURNS TABLE).

• Use a named variable instead of ALIAS. Simpler, doing the same, and it's the preferred way.

• A simple function like this could also be written in LANGUAGE sql:

CREATE OR REPLACE FUNCTION get_names(_tname varchar)
  RETURNS TABLE (col_a integer, col_b text) AS
$func$
SELECT t.col_a, t.col_b  --, more columns - must match RETURNS above
FROM   mytable t
WHERE  t.name = $1;
$func$ LANGUAGE sql;