delete from tb_table where id not in (select maxid from (select max(id) as maxid from tb_table group by sample_code) b);
tb_table:表名；
id，sample_code：列名
mysql 删除重复记录，只保留id字段值最大的记录
原文：https://www.cnblogs.com/zyh-C/p/10491374.html
