sql删除重复数据只保留一条

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（Id）来判断
 
select * from 表 where Id in (select Id from 表 group byId having count(Id) > 1)
 
2、删除表中多余的重复记录，重复记录是根据单个字段（Id）来判断，只留有rowid最小的记录
 
DELETE from 表 WHERE (id) IN ( SELECT id FROM 表 GROUP BY id HAVING COUNT(id) > 1) AND PID NOT IN (SELECT MIN(PID) FROM 表 GROUP BY id HAVING COUNT(*) > 1);
 
3、查找表中多余的重复记录（多个字段）
 
select * from 表 a where (a.Id,a.seq) in(select Id,seq from 表 group by Id,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 表 a where (a.Id,a.seq) in (select Id,seq from 表 group by Id,seq having count(*) > 1) and PID not in (select min(PID) from 表 group by Id,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 表 a where (a.Id,a.seq) in (select Id,seq from 表 group by Id,seq having count(*) > 1) and PID not in (select min(PID) from 表 group by Id,seq having count(*)>1)