MySql数据库查询某个列的重复值

MySql数据库查询某个列的重复值（vc_name：要查询的重复字段，xm_position：要查询的表名）

select vc_name,count(*) as count from xm_position group by vc_name having count>1;

删除所查询出来多于的重复值，最大的ID留下，删除其它所有重复的

DELETE FROM xm_position WHERE id NOT IN (SELECT dt.minno FROM (SELECT MAX(id) AS minno FROM xm_position GROUP BY vc_name) dt);