查询及删除重复记录的方法

删除一个字段重复的记录SQL语句
  Delete T From
  (Select Row_Number() Over(Partition By STime order By STime) As RowNumber,* From DH1002)T
  Where T.RowNumber > 1

 (一)
  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
  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
  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)
  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
  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
  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)
 (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 for select 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
  set rowcount @max
  delete from 表名 where 主字段 = @id
  fetch cur_rows into @id,@max
  end
  close cur_rows
  set rowcount 0
  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
  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
  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
  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)
  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
  )
  3、查找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)
  运行会产生问题,where(a.peopleId,a.seq)这样的写发是通不过的!

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