oracle 修改某字段小数位精度 须要字段未empty的解决办法

执行：alter table bosp_htjs_material_information modify taxrate number(16,3);
直接执行若是有数据会有报错：ORA-01440: column to be modified must be empty to decrease precision or scale

数据不是很是大的状况下解决办法：1.备份表数据，2.清空原表对应列 3.修改字段精度。4.同步更新数据值。5.截断备份的临时表并删除

--1.create table BOSP_HTJS_MATERIAL_BAK as select * from BOSP_HTJS_MATERIAL_INFORMATION;
 select * from BOSP_HTJS_MATERIAL_BAK;
 
 --2.update BOSP_HTJS_MATERIAL_INFORMATION MI set MI.FEED_NUM = null;
  select * from BOSP_HTJS_MATERIAL_INFORMATION;

 --3.alter table BOSP_HTJS_MATERIAL_INFORMATION modify FEED_NUM number(16,3);

 --4.update BOSP_HTJS_MATERIAL_INFORMATION MI set MI.FEED_NUM = (
    select MB.FEED_NUM from BOSP_HTJS_MATERIAL_BAK MB where MB.id = MI.id
 );

 --5.truncate table  BOSP_HTJS_MATERIAL_BAK;drop table BOSP_HTJS_MATERIAL_BAK;