Creating Custom columns in stored procedure postgres - sql

Question

I am using a stored procedure to return the type of student that is enrolled at my college. Pushing their ID through should return their first name and last name in a new column that is going to be made(Ex: commuter, employee, resident). I keep getting an error:
ERROR: syntax error at or near "if"
LINE 8: if exists (select count(commuterid) > 0 from commuter wh...).
Any tips or ideas?
create or replace function roleAtMarist(int, REFCURSOR) returns refcursor as
$$
declare
identifier int := $1;
resultset refcursor := $2;
begin
open resultset for
if exists (select count(commuterid) > 0 from commuter where commuterid = identifier) then
select fname, lname, "Commuter" as Role
from people
where peopleid = identifier;
end if;
if exists (select count(employeeid) > 0 from employee where emplpoyeeid = identifier) then
select fname, lname, "Employee" as Role
from people
where peopleid = identifier;
end if;
if exists (select count(residentid) > 0 from studentpark where residentid = identifier) then
select fname, lname, "Resident" as Role
from people
where peopleid = identifier;
end if;
return resultset;
end;
$$
language plpgsql;
select roleAtMarist(12, 'resultset') ;
fetch all from results ;

Answer 1

This is backwards in multiple ways. A cursor would use valid SQL and no plpgsql commands. But you don't need a cursor nor plpgsql to begin with. A simple SQL function should do:
CREATE OR REPLACE FUNCTION role_at_marist(_identifier int)
RETURNS TABLE (fname text, lname text, "role" text) AS
$func$
SELECT p.fname, p.lname, text 'Commuter'
FROM people
WHERE p.peopleid = $1
AND EXISTS (SELECT 1 FROM commuter c WHERE c.commuterid = p.peopleid)
UNION ALL
SELECT p.fname, p.lname, 'Employee'
FROM people
WHERE p.peopleid = $1
AND EXISTS (SELECT 1 FROM employee e WHERE e.emplpoyeeid = p.peopleid)
UNION ALL
SELECT p.fname, p.lname, 'Resident'
FROM people
WHERE p.peopleid = $1
AND EXISTS (SELECT 1 FROM studentpark s WHERE s.residentid = p.peopleid)
$func$ LANGUAGE sql;
Call:
SELECT * FROM role_at_marist(12);
Set-returning functions can be used just like tables in the FROM list.
String literals are enclosed in single quotes!