Oracle查询并删除重复记录的SQL语句

  • 来源: IT实验室 作者: sevenleaf   2010-07-20/10:43
  •       查询及删除重复记录的SQL语句

          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)

          注:rowid为oracle自带不用该.....

          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

          "重复记录"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

          )


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