sql语句之查询与删除重复数据

1、查询表中重复数据（单字段）
Select * From 表 Where 字段1 In (Select 字段1 From 表 Group By 字段1 Having Count(字段1) > 1)

 

2、删除表中多余的重复记录，只留有rowid最小的记录（单字段）
Delete From 表
Where 字段1 In (Select 字段1 From 表 Group By 字段1 Having Count(字段1) > 1) And
   Rowid Not In (Select Min(Rowid) From 表 Group By 字段1 Having Count(字段1) > 1)
     

3、查找表中多余的重复记录（多个字段） 
Select * From 表 a Where (a.字段1, a.字段2) In (Select 字段1, 字段2 From 表 Group By 字段1, 字段2 Having Count(*) > 1)

4、删除表中多余的重复记录，只留有rowid最小的记录（多个字段）
Delete From 表 a
Where (a.字段1, a.字段2) In (Select 字段1, 字段2 From 表 Group By 字段1, 字段2 Having Count(*) > 1) And
   Rowid Not In (Select Min(Rowid) From 表 Group By 字段1, 字段2 Having Count(*) > 1)
      
5.删除多于的重复记录（单个字段，多个字段）
delete from table where id not in ( select min(id) from table group by name)
或者
delete from table where id not in ( select min(id) from table group by 字段1，字段2)

6.删除多余的重复记录（单个字段，多个字段）
delete from table where id in ( select max(id) from table group by name 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 表 a
Where (a.字段1, a.字段2) In (Select 字段1, 字段2 From 表 Group By 字段1, 字段2 Having Count(*) > 1) And
   Rowid Not In (Select Min(Rowid) From 表 Group By 字段1, 字段2 Having Count(*) > 1)

查单个字段的重复次数
Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1