create or replace trigger MYSWITCHENROLL
after update of classnumber on revenroll
for each row
begin
	update revclass
	set currentenroll=currentenroll+1
	where revclass.classnumber=:new.classnumber;
	update revclass
	set currentenroll=currentenroll-1;

exception
	when NO_DATA_FOUND then 
		DBMS_OUTPUT.PUT_LINE('No data found');
	when others then
		DBMS_OUTPUT.PUT_LINE('Error-' || SQLERRM);
END;

/
