使用SQL命令的in&not in等删除数据的总结
内容导读
互联网集市收集整理的这篇技术教程文章主要介绍了使用SQL命令的in&not in等删除数据的总结,小编现在分享给大家,供广大互联网技能从业者学习和参考。文章包含1868字,纯文字阅读大概需要3分钟。
内容图文
* from my_test_table where id not in (select b.id as id from ( SELECT MAX(a.`ModifyAt`)ModifyAt,a.userid FROM my_test_table a GROUP BY a.UserId,a.SeriesId,a.CourseId) c INNER JOIN `my_test_table` b ON c.userid=b.userid AND c.ModifyAt=b.ModifyAt)优化后:
select * from (select u.id as id from my_test_table u left join (select b.id as id from ( SELECT MAX(a.`ModifyAt`)ModifyAt,a.userid FROM my_test_table a GROUP BY a.UserId,a.SeriesId,a.CourseId) c INNER JOIN `my_test_table` b ON c.userid=b.userid AND c.ModifyAt=b.ModifyAt) d on d.id = u.id where d.Id is null) as e
2、查询出后,需要用 delete where in 来删除,但是delete where in 语句效率极其低下。
原语句:
delete from my_test_table where id in (select * from (select u.id as id from my_test_table u left join (select b.id as id from ( SELECT MAX(a.`ModifyAt`)ModifyAt,a.userid FROM my_test_table a GROUP BY a.UserId,a.SeriesId,a.CourseId) c INNER JOIN `my_test_table` b ON c.userid=b.userid AND c.ModifyAt=b.ModifyAt) d on d.id = u.id where d.Id is null) as e)
因此改为where语句,关联表删除数据 优化后:
delete deluser from my_test_table deluser,(select * from (select u.id as id from my_test_table u left join (select b.id as id from ( SELECT MAX(a.`ModifyAt`)ModifyAt,a.userid FROM my_test_table a GROUP BY a.UserId,a.SeriesId,a.CourseId) c INNER JOIN `my_test_table` b ON c.userid=b.userid AND c.ModifyAt=b.ModifyAt) d on d.id = u.id where d.Id is null) as e) f where deluser.id = f.id;
0.36秒执行完成。
参考文章:
https://blog.csdn.net/hello_l/article/details/71419464
https://blog.csdn.net/pcwblover008/article/details/80015855
使用SQL命令的in¬ in等删除数据的总结
标签:href code series color log 优化 not 结合 mod
本文系统来源:https://www.cnblogs.com/dayang12525/p/12751123.html
内容总结
以上是互联网集市为您收集整理的使用SQL命令的in&not in等删除数据的总结全部内容,希望文章能够帮你解决使用SQL命令的in&not in等删除数据的总结所遇到的程序开发问题。 如果觉得互联网集市技术教程内容还不错,欢迎将互联网集市网站推荐给程序员好友。
内容备注
版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 gblab@vip.qq.com 举报,一经查实,本站将立刻删除。
内容手机端
扫描二维码推送至手机访问。