zoukankan      html  css  js  c++  java
  • leetcode 删除一张表中重复邮箱的数据,并且保留最小id 的 那条

    /*
    create view testview as SELECT subject,MIN(Id) as id FROM test GROUP BY subject;
    select * FROM test WHERE id not in (SELECT id FROM testview);
    */
    mysql> select * from test;
    +----+------------+-------+-----------+
    | id | name       | score | subject   |
    +----+------------+-------+-----------+
    |  1 | xiaoming   |    89 | shuxue    |
    |  2 | xiaohong   |    89 | shuxue    |
    |  3 | xiaohong   |    80 | english   |
    |  4 | xiaohong   |    80 | physics   |
    |  5 | xiaohong   |    80 | astronaut |
    |  6 | xiaoming   |    80 | physics   |
    |  7 | xiaoming   |    80 | astronaut |
    |  8 | xiaoming   |    80 | english   |
    |  9 | xiaobai    |    80 | astronaut |
    | 10 | 1.2xiaobai |    80 | english   |
    | 11 | 2.2xiaobai |    80 | physics   |
    | 12 | 3xiaobai   |    80 | shuxue    |
    | 13 | 123xiaohei |    80 | astronaut |
    | 14 | xiaohei    |    80 | shuxue    |
    | 15 | xiaohei    |    80 | physics   |
    | 16 | .12xiaohei |    80 | english   |
    +----+------------+-------+-----------+
    16 rows in set (0.00 sec)
    
    
    
    mysql> create view testview as SELECT subject,MIN(Id) as id FROM test GROUP BY subject;
    Query OK, 0 rows affected (0.01 sec)
    
    
    
    mysql> select * FROM test WHERE id not in (SELECT id FROM testview);               +----+------------+-------+-----------+
    | id | name       | score | subject   |
    +----+------------+-------+-----------+
    |  2 | xiaohong   |    89 | shuxue    |
    |  6 | xiaoming   |    80 | physics   |
    |  7 | xiaoming   |    80 | astronaut |
    |  8 | xiaoming   |    80 | english   |
    |  9 | xiaobai    |    80 | astronaut |
    | 10 | 1.2xiaobai |    80 | english   |
    | 11 | 2.2xiaobai |    80 | physics   |
    | 12 | 3xiaobai   |    80 | shuxue    |
    | 13 | 123xiaohei |    80 | astronaut |
    | 14 | xiaohei    |    80 | shuxue    |
    | 15 | xiaohei    |    80 | physics   |
    | 16 | .12xiaohei |    80 | english   |
    +----+------------+-------+-----------+
    12 rows in set (0.00 sec)
    
    

    参考:

    https://www.cnblogs.com/justdo-it/articles/8480460.html

  • 相关阅读:
    基于maven的profile实现动态选择配置文件
    [公告]博客迁移通知
    itellij idea导入web项目并部署到tomcat
    DWR实现后台推送消息到web页面
    DWR实现扫一扫登录功能
    微信企业号开发[目录]
    微信企业号开发[一]——创建应用
    微信企业号开发[三]——调用微信接口
    微信企业号开发[二]——获取用户信息
    JavaScript编码规范指南
  • 原文地址:https://www.cnblogs.com/sea-stream/p/11351238.html
Copyright © 2011-2022 走看看