How to reduce functions with simple select query?

Question

I have a function to identify the root parent of a particular id. I use this in function in select query,which invokes function for every row in table.I need to merge the function inside the query itself.Please suggest  me.
Function
CREATE OR REPLACE FUNCTION fnroot(v_id int ) return int as
v_left int;
v_right int;
v-result int;
begin
select left,right into v_left,v_right from sam where id=v_id;
select id into v_result from sam
where id in (select id from mst m where m.depth=2 )
and left < v_left and right > v_right;
return v_result;
end
query:
select fnroot(s.id) from master s;

Answer 1

Hi,
Ramin's idea is very good. You must use joins in function as below
CREATE OR REPLACE FUNCTION fnroot(v_id int ) return int as
    v_result int;
Begin
select  s.id into v_result
  from sam s on s.id = v_id
           left join sam s2 on (s2.id in (select id from mst m where m.depth = 2) and s2.left < s.left and s2.right > s.right)
return v_result;
End;
Regards
Mahir M. Quluzade