Java J2ee Planet

The table containing the foreign key is called the   referencing   or   child table , and the table containing the candidate key is called the   referenced   or   parent table .   SET NULL   : Sets the column value to   NULL   when you delete the parent table row. CASCADE   : CASCADE will   propagate the change   when the parent changes. If you delete a row, rows in constrained tables that reference that row   will also be deleted , etc.