plpgsql how to just execute query in a function or procedure - sql

Question

I am beginning to learn stored procedures and functions in sql in a postgres database.
I need an example to get me going for what I am trying to accomplish.
I need to run a procedure and have it return results. For example something like this:
run_query(name):
begin
return select * from employees where first_name = $name
end
end
I want something like the above to return the result set when I run it. Is this possible? thank you for your help in advance!
Here is the function im trying to create:
CREATE OR REPLACE FUNCTION test() RETURNS TABLE(id INT, subdomain varchar, launched_on_xxx timestamp, UVs bigint, PVs bigint) AS
'SELECT dblink_connect(''other_DB'');
SELECT c.id as id, c.subdomain, c.launched_on_xxx, COALESCE(SUM(tbd.new_unique_visitors), 0) AS UVs, COALESCE(SUM(tbd.page_views), 0) AS PVs
FROM dblink(''SELECT id, subdomain, launched_on_xxx FROM communities'')
AS c(id int, subdomain character varying, launched_on_xxx timestamp)
LEFT OUTER JOIN days_of_center tbd
ON c.id = tbd.community_id
WHERE c.launched_on_xxx < now()
GROUP BY c.id, c.subdomain, c.launched_on_xxx;
SELECT dblink_disconnect();'
LANGUAGE SQL;

Answer 1

Your function could look like this:
CREATE OR REPLACE FUNCTION test()
RETURNS TABLE(id int, subdomain varchar, launched_on_xxx timestamp
,uvs bigint, pvs bigint) AS
$func$
SELECT dblink_connect('other_DB');
SELECT c.id
,c.subdomain
,c.launched_on_xxx
,COALESCE(SUM(tbd.new_unique_visitors), 0) AS uvs
,COALESCE(SUM(tbd.page_views), 0) AS pvs
FROM dblink('
SELECT id, subdomain, launched_on_xxx
FROM communities
WHERE launched_on_xxx < now()')
AS c(id int, subdomain varchar, launched_on_xxx timestamp)
LEFT JOIN days_of_center tbd ON tbd.community_id = c.id
GROUP BY c.id, c.subdomain, c.launched_on_xxx;
SELECT dblink_disconnect();
$func$ LANGUAGE SQL;
Pull the WHERE clause down into the dblink function. It's much more effective not to fetch rows to begin with - instead of fetching them from the external database and then discarding them.
Use dollar-quoting to avoid confusion with quoting. That has become standard procedure with bigger function definitions.
To output it in "table format", call a function returning multiple columns like this:
SELECT * FROM test();

Answer 2

Just about the simplest possible example would be this;
CREATE FUNCTION test() RETURNS TABLE(num INT) AS
'SELECT id FROM table1'
LANGUAGE SQL;
SELECT * FROM test()
An SQLfiddle to test with.
If you need a parameter, here's another example;
CREATE FUNCTION test(sel INT) RETURNS TABLE(val VARCHAR) AS
'SELECT value FROM table1 WHERE id=sel'
LANGUAGE SQL;
SELECT * FROM test(2)
Another SQLfiddle to test with.