sql中的排序倒序
排序采用 order by 子句,order by 后面跟上排序字段,排序字段可以放多个,多个采用逗号间隔,order by默认采用升序(asc),如果存在 where 子句,那么 order by 必须放到where 语句后面。
*select jlwbdh from YSKD order by jlwbdh desc
SQL查询某一字段重复的数据
*select jlwbdh from YSKD group by jlwbdh having count(jlwbdh)>1;