ORA-01440 要减小精度或者标度.则要修改的列必须为空.

--1 创建备份表
drop table contract_kangjia_back;
create table contract_kangjia_back
as 
select *　from contract_kangjia;
--2 将原有表的数据删除
delete from contract_kangjia;
--3 改变原有表的数据结构
alter table contract_kangjia modify sell_money  number(10,5) ;
--4 将原有表的数据插入新的表
insert into contract_kangjia
  (id, busiman_name, sell_date, product_type, sell_money)
  select  id, busiman_name, sell_date, product_type, sell_money 
    from contract_kangjia_back;