MySql 删除多个字段重复的数据（只保留一条）

DELETE FROM 表名 WHERE (字段1,字段2,字段3)
IN 
(SELECT 字段1,字段2,字段3 FROM (SELECT 字段1,字段2,字段3 FROM 表名 GROUP BY 字段1,字段2,字段3 HAVING COUNT(*)>1) s1) 
AND
id NOT IN (SELECT id FROM (SELECT id FROM 表名 GROUP BY 字段1,字段2,字段3 HAVING COUNT(*)>1) s2);