-- Add/modify columns 
alter table T_CASE add BACKFEE number(10,2);
alter table T_CASE add REALBACKPRICE number(10,2);
-- Add comments to the columns 
comment on column T_CASE.BACKFEE
  is '退款手續(xù)費';
comment on column T_CASE.REALBACKPRICE
  is '實際退款金額';