1、表结构与数据：
CREATE TABLE tablezzl( id int, name VARCHAR(255) );
2、查询出重复的数据：
SELECT name FROM tablezzl GROUP BY name HAVING COUNT(name)>1
3、查询出要保留的重复数据：
SELECT MIN(id) ids FROM tablezzl GROUP BY NAME HAVING COUNT(name)>1
4、最终的SQL：
DELETE FROM tablezzl WHERE 1=1 AND `name` in (SELECT * FROM ( (SELECT `name` `names` FROM tablezzl GROUP BY name HAVING COUNT(`name`)>1) ) a) AND id not in (SELECT * FROM ( (SELECT MIN(id) ids FROM tablezzl GROUP BY NAME HAVING COUNT(`name`)>1) ) b)
5、补充 ：
其中这样写mysql中不能如下这样写：
DELETE FROM tablezzl WHERE 1=1 AND `name` in (SELECT `name` `names` FROM tablezzl GROUP BY name HAVING COUNT(`name`)>1) AND id not in (SELECT MIN(id) ids FROM tablezzl GROUP BY NAME HAVING COUNT(`name`)>1)
会报错：You can‘t specify target table ‘tablezzl‘ for update in FROM clause，不能在同一表中查询的数据作为同一表的更新数据，如模块4的SQL包装一下就可以解决。
原文：https://www.cnblogs.com/java-zzl/p/9739750.html