其它互联网摘抄：
1、写一张表中有id和name 两个字段，查询出name重复的所有数据，现在列下：
select * from xi a where (a.username) in (select username from xi group by username having count(*) > 1)
2、查询出所有数据进行分组之后，和重复数据的重复次数的查询数据，先列下：
select count(username) as ’重复次数’,username from xi group by username having count(*)>1 order by username desc
3、一下为 查看别人的 结果，现列下：查询及删除重复记录的方法大全
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 integerdeclare cur_rows cursor local for select 主字段,count(*) from 表名 group by 主字段 having count(*) >； 1open cur_rowsfetch cur_rows into @id,@maxwhile @@fetch_status=0beginselect @max = @max -1set rowcount @maxdelete from 表名 where 主字段 = @idfetch cur_rows into @id,@maxendclose cur_rowsset 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 tableNamedrop table tableNameselect * into tableName from #Tmpdrop 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 tableNameselect min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoIDselect * 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 tablenamegroup by idhaving count(id) > 1)
*******举例*********
查询 Sap Business One制造商OMRC表中重复数据(Pass)
select * from omrc
where firmname in (select firmname from omrc group by firmname having count(firmname) > 1)
删除 Sap Business One制造商OMRC表中重复数据(Pass)
delete from omrc
where FirmName in (select FirmName from omrc group by FirmName having count(FirmName) > 1)
and FirmCode not in (select min(FirmCode) from omrc group by FirmName having count(FirmName )>1)
OMRC为表名，FirmName/FirmCode为字段名。
***删除或保留一些行数据
数据库int001几个表OMRC/POR1/RDR1，保留前六行数据(操作，出现表错误，处理后/truncate/再导入)
DELETE OMRC WHERE FirmCode NOT IN(SELECT TOP 6 FirmCode FROM OMRC)
DELETE Por1 WHERE DocEntry NOT IN(SELECT TOP 6 DocEntry FROM Por1)
DELETE RDR1 WHERE DocEntry NOT IN(SELECT TOP 6 DocEntry FROM RDR1)
*****************************
查询数据库中带有某个字段的所有表名
MySQL数据库查询带有某个字段的所有表名：
（1）精确查询语句如下：
SELECT * FROM information_schema.columns WHERE column_name=’column_name’
（2）模糊匹配查询
SELECT * FROM information_schema.columns WHERE column_name LIKE ’%column_name%’
Oracle数据库查询带有某个字段的所有表名：
（1）精确查询语句如下：
SELECT column_name,table_name FROM user_tab_columns WHERE column_name=’column_name’
（2）模糊匹配查询
SELECT column_name,table_name,FROM user_tab_columns WHERE column_name LIKE ’%column_name%’
SQLServer数据库查询带有某个字段的所有表名：
（1）精确查询语句如下：
SELECT [name] FROM [库名].[dbo].sysobjects WHERE id IN (SELECT id FROM [库名].[dbo].syscolumns WHERE name = ’字段名’)
（2）模糊匹配查询
SELECT [name] FROM [库名].[dbo].sysobjects WHERE id IN (SELECT id FROM [库名].[dbo].syscolumns WHERE name LIKE ’%字段名%’)
