sql 查表重复数据，删除重复数据保留一条记录

1、sql 查表重复数据  

Select * From 表XX Where user_id In (Select user_id From 表XX Group By user_id Having Count(*)>1) 

2、sql 查表重复数据  

Select user_id From 表XX  Group By user_id Having Count(*)>1

删除重复数据保留一条记录  保留一条

DELETE FROM 表XX  WHERE user_id IN (select user_id from (
SELECT user_id FROM 表XX GROUP BY user_id HAVING COUNT(*) > 1) a ) 
AND id NOT IN (select id from ( SELECT min(id) id FROM 表XX GROUP BY user_id HAVING count(id) > 1) b