| 标题 | sql查询重复记录、删除重复记录方法大全 |
| 范文 | 查找所有重复标题的记录： ? 1 SELECT * FROM t_info a WHERE ((SELECT COUNT(*) FROM t_info WHERE Title = a.Title) > 1) ORDER BY Title DESC 一、查找重复记录 1、查找全部重复记录 ? 1 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) ? 1 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) ? 1 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 ^_^) ? 1 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 三、举例 1、查找表中多余的重复记录，重复记录是根据单个字段(peopleId)来判断 ? 1 select * from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1) 2、删除表中多余的重复记录，重复记录是根据单个字段(peopleId)来判断，只留有rowid最小的记录 ? 1 2 delete from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1) and rowid not in (select min(rowid) from people group by peopleId having count(peopleId )>1) 3、查找表中多余的重复记录(多个字段) ? 1 select * from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) 4、删除表中多余的重复记录(多个字段)，只留有rowid最小的记录 ? 1 2 delete from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1) 5、查找表中多余的重复记录(多个字段)，不包含rowid最小的记录 ? 1 2 select * from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1) 四、补充 有两个以上的重复记录，一是完全重复的记录，也即所有字段均重复的记录，二是部分关键字段重复的记录，比如Name字段重复，而其他字段不一定重复或都重复可以忽略。 1、对于第一种重复，比较容易解决，使用 ? 1 select distinct * from tableName 就可以得到无重复记录的结果集。 如果该表需要删除重复的记录(重复记录保留1条)，可以按以下方法删除 ? 1 2 3 4 select distinct * into #Tmp from tableName drop table tableName select * into tableName from #Tmp drop table #Tmp 发生这种重复的原因是表设计不周产生的，增加唯一索引列即可解决。 2、这类重复问题通常要求保留重复记录中的第一条记录，操作方法如下 假设有重复的字段为Name,Address，要求得到这两个字段唯一的结果集 ? 1 2 3 select identity(int,1,1) as autoID, * into #Tmp from tableName select min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoID select * from #Tmp where autoID in(select autoID from #tmp2) |
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