Postgresql get single column of row in for loop - postgresql

Question

This is probably really easy, but its driving me crazy.
I have the following function:
CREATE OR REPLACE FUNCTION get_group(serverid BIGINT, name VARCHAR(100)) RETURNS BIGINT
LANGUAGE plpgsql
AS $$
DECLARE
group server_groups%ROWTYPE;
BEGIN
FOR group IN SELECT * FROM server_groups WHERE server_id = serverid AND LOWER(group_name) = LOWER(name) LOOP
RETURN group.id;
END LOOP;
RETURN 0;
END;
$$;
And the following tables:
server
server_id | server_name
----------+---------------
3251623 | ServerOfDoom
5578921 | BestServerEU
server_groups
id | server_id | group_name
---+----------+---------------
1 | 3251623 | aNiceGroup
2 | 5578921 | Valorant
3 | 5578921 | Admins
But when executing my function query I get the following error:
ERROR: syntax error at or near "."
LINE 8: RETURN group.id;
I get that this means I can't just get the id of the group row by saying group.id, but I'm really going crazy finding out how after visiting 100 different sites (maybe I'm just a bad Googler)
How do I get a single attribute of a row in a for loop?

Answer 1

You are overcomplicating things. Your requirement can be achieved with a single SQL query (which can be wrapped in a SQL function):
CREATE OR REPLACE FUNCTION get_group(serverid BIGINT, name VARCHAR(100))
RETURNS BIGINT
as
$$
select coalesce(max(id), 0) as id
from server_groups
where server_id = serverid
and lower(group_name) = lower(name);
$$
language sql
stable;
If the WHERE clause returns no match, max(id) will yield null and the coalesce() will turn that into a 0 (although I would think a null would make much more sense).
If the WHERE clauses matches a row, the query will return the highest ID. As you only expect a single row from the query, the aggregate function won't change that.
If you really want that to be a PL/pgSQL function, you can use the FOUND status as shown in the manual:
CREATE OR REPLACE FUNCTION get_group(serverid BIGINT, name VARCHAR(100))
RETURNS BIGINT
AS $$
declare
group_id int;
BEGIN
select id
into group_id
from server_groups
where server_id = serverid
and lower(group_name) = lower(name);
if found then
return group_id;
else
return 0;
end if;
END;
$$
LANGUAGE plpgsql;