MySQL根据某一个或者多个字段查找/删除重复数据

SELECT * FROM table WHERE 字段 IN (
 SELECT 字段 FROM tb_table GROUP BY 字段 HAVING COUNT(字段) > 1
);

SELECT * FROM (SELECT *, CONCAT(字段1,字段2) as 字段1And字段2 FROM table) a WHERE a.字段1And字段2 IN (
 SELECT 字段1And字段2 FROM (SELECT CONCAT(字段1,字段2) as 字段1And字段2 FROM table) b GROUP BY 字段1And字段2 HAVING COUNT(字段1And字段2) > 1
)

DELETE FROM table WHERE id not IN (
 SELECT maxid FROM (SELECT max(id) as maxid FROM table group by 字段) b
);

DELETE FROM table WHERE id not IN (
 SELECT maxid FROM (SELECT MAX(id) as maxid, CONCAT(字段1,字段2) as 字段1And字段2 FROM table GROUP BY 字段1And字段2) t
);