Oracle 18c

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create table employees (first_name varchar2(20), salary number, department_id varchar2(20));
insert into employees
select 'Emp1', 10, '1' from dual
union all
select 'Emp2', 20, '1' from dual
union all
select 'Emp3', 25, '1' from dual
3 rows affected

CREATE OR REPLACE FUNCTION get_status(
    v_name IN employees.first_name%TYPE
) return boolean IS
    v_compare number(1);
BEGIN
    select case when e1.salary < (select avg(salary) from employees e2 where e2.department_id = e1.department_id) then 0 else 1 end
    into v_compare
    from employees e1
    where e1.first_name = v_name;
    
    return v_compare = 1;
END;
/

BEGIN
 if(get_status('Emp1')=true) then
 dbms_output.put_line('high salary');
 else
  dbms_output.put_line('low salary');
 end if;
END;
/
1 rows affected

dbms_output:
low salary