Question

I have function that receives department name and an aggregation operation (average, maximum, minimum) and applies the operation on the salary of employees working on the given department and return the result

create or replace
function salaryData (p_depname varchar2, p_aggr_op varchar2)
return number
is
  v_aggrr_op varchar2(20);
  v_sal_max number;
  v_sal_min number;
  v_sal_avg number;
begin
  select max(e.salary), min(e.salary), avg(e.salary)
  into v_sal_max, v_sal_min, v_sal_avg
  from employee e join department d
  on e.deptno=d.deptno
  where d.deptname=p_depname;
  if p_aggr_op in ('max','MAX') then
    return v_sal_max;
  end if;

  if p_aggr_op in ('min','MIN') then
    return v_sal_min;
  end if;

  if p_aggr_op in ('avg','AVG') then
    return v_sal_avg;
  end if;
end salaryData;
/ 

when i use function call

select salaryData('FINANCE','max') as max_sal from employee;

i got the ouput like:

max_sal|
-------|
20000  |
20000  |
20000  |
20000  |
20000  |
-------

how can i show that this is the maximum salary of employeeid, employeename working in departmentname

Answer 1

select salaryData('FINANCE','max') as max_sal from dual;

Dual exists to allow you to run functions once in sql.