suzi

摘要： 假如有一张users表,里面有user_id,user_name两个字段,用一条sql语句去掉数据库里的userName重复的记录.1.delete from users a where a.user_id = (select max(b.user_id) from users b where a.user_name=b.user_name);这一种自联接,效率低一点.2.delete from ... 阅读全文