oracle 行触发器

create or replace trigger purorder_residue_quantity
AFTER UPDATE OF FTOTALRECEIPTQTY
ON eas.t_Sm_Purorderentry 
FOR EACH ROW
begin
  update eas.T_SM_PurOrderEntry set CFRESIDUALQUANTITY=FQTY-FTOTALRECEIPTQTY   where  FID=:new.FID;
 END;