removed a line from the collection only:
SQL> select po1_0.id,po1_0.customer from PurchaseOrder po1_0 where po1_0.id=?
SQL> select l1_0.order_id,l1_0.id,l1_0.sku from OrderLine l1_0 where l1_0.order_id=?
SQL> delete from OrderLine where id=?
removed the order (cascade ALL):
SQL> select po1_0.id,po1_0.customer from PurchaseOrder po1_0 where po1_0.id=?
SQL> select l1_0.order_id,l1_0.id,l1_0.sku from OrderLine l1_0 where l1_0.order_id=?
SQL> delete from OrderLine where id=?
SQL> delete from PurchaseOrder where id=?