procedure USER_NAME is
    num1 Number;
begin
    select count(1)
	into num1
        from dept
        where deptno = :dept.deptno
	and (:dept.rowid is null or
	     :dept.rowid != rowid);

---i dont understand why they check like this and it is a table 
-- and not a view.
---can someone throw light on this as what this code does?
	    
    if (num1 > 0) then
        message('it is wrong');       
         raise form_trigger_failure;
    end if;

end USER_NAME ;