查询表中相同数据的sql语句

今天药忘吃喽~ 2022-09-18 12:54 252阅读 0赞

--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)