sql记录去重（SQL查询或者删除表中重复记录）
1、查表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断
select*from people
where peopleId in (select peopleId from people groupby 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
deletefrom people
where peopleId in (select peopleId from people groupby peopleId having count(peopleId)>1)
and rowid notin (select min(rowid)from people group by peopleId having count(peopleId )>1)
3、查表中多余的重复记录（多个字段）
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
deletefrom vitae a
where (a.peopleId,a.seq)in (select peopleId,seq from vitae group by peopleId,seq having count(*)>1)
and rowid notin (select min(rowid)from vitae group by peopleId,seq having count(*)>1)
5、查表中多余的重复记录（多个字段），不包含rowid最⼩的记录
select*from vitae a
where (a.peopleId,a.seq)in (select peopleId,seq from vitae group by peopleId,seq having count(*)>1)
and rowid notin (select min(rowid)from vitae group by peopleId,seq having count(*)>1)
(⼆)
⽐⽅说
在A表中存在⼀个字段“name”，
⽽且不同记录之间的“name”值有可能会相同，
现在就是需要查询出在该表中的各记录之间，“name”值存在重复的项；
Select Name,Count(*)From A Group By Name Having Count(*)>1
如果还查性别也相同⼤则如下:
Select Name,sex,Count(*)From A Group By Name,sex Having Count(*)>1
(三)
⽅法⼀
declare@max integer,@id integer
declare cur_rows cursor local forselect主字段,count(*)from表名group by主字段having count(*)>；1
open cur_rows
fetch cur_rows into@id,@max
while@@fetch_status=0
begin
select@max=@max-1
setrowcount@max
deletefrom表名where主字段=@id
fetch cur_rows into@id,@max
end
close cur_rows
setrowcount0
  ⽅法⼆
  有两个意义上的重复记录，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
selectdistinct*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
  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
selectdistinct*into #Tmp from tableName
droptable tableName
select*into tableName from #Tmp
select distinct fromdroptable #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
select identity(int,1,1)as autoID, *into #Tmp from tableName
select min(autoID)as autoID into #Tmp2from #Tmp groupby Name,autoID
select*from #Tmp where autoID in(select autoID from #tmp2)
  最后⼀个select即得到了Name，Address不重复的结果集（但多了⼀个autoID字段，实际写时可以写在select⼦句中省去此列）
(四)查询重复
select*from tablename where id in (
select id from tablename
group by id
having count(id)>1
)

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