Sql 学习记录 一种删除重复数据的方法

select identity(int,1,1) as autoID, columnName ,count( columnName) sum into #temp from tableName
group by  columnName
having count( columnName) > 1
// 查处columnName这一列重复的数据，并保存在一张临时表#temp中,且添加了autoID字段

select * from #temp   //查看临时表的数据
delete tableName where  columnName in (
Select  columnName from #temp
)
//删除表中的重复全部数据，一行不留

insert into tableName( columnName)
Select  columnName from #temp
//插入重复数据，使得重复数据保留一行

select  columnName from tableName group by  columnName
Having count( columnName)>1
//查看结果
drop table #temp
//删除临时表