SQL重复记录处理(查找,过滤,删除)

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= * = = * = = * = = * = = * = = * = = * = = * = = * = = * = = * = = *

注：此处“重复”非完全重复,意为某字段数据重复

HZT表结构

ID              int

Title          nvarchar(50)

AddDate  datetime

数据

一。查找重复记录

1。查找全部重复记录

Select * From 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)

2。过滤重复记录(只显示一条)

Select * From HZT Where ID In (Select Max(ID) From HZT Group By Title)

注：此处显示ID最大一条记录

二。删除重复记录

1。删除全部重复记录（慎用）

Delete 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)

2。保留一条（这个应该是大多数人所需要的 ^_^）

Delete HZT Where ID Not In (Select Max(ID) From HZT Group By Title)

注：此处保留ID最大一条记录