Database LeetCode Employees Earning More Than Their Managers

最新推荐文章于 2019-03-05 10:04:07 发布

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最新推荐文章于 2019-03-05 10:04:07 发布

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分类专栏： Mysql数据库文章标签： MySQL leetcode

本文链接：https://blog.youkuaiyun.com/sun_wangdong/article/details/50682498

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本文介绍了一种SQL查询技巧，通过自连接的方式找出薪资高于其直接上司的员工名单。利用内连接和不等值连接，实现了从单一员工表中筛选出符合条件的数据。

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题目：

The Employee table holds all employees including their managers. Every employee has an Id, and there is also a column for the manager Id.

+----+-------+--------+-----------+
| Id | Name  | Salary | ManagerId |
+----+-------+--------+-----------+
| 1  | Joe   | 70000  | 3         |
| 2  | Henry | 80000  | 4         |
| 3  | Sam   | 60000  | NULL      |
| 4  | Max   | 90000  | NULL      |
+----+-------+--------+-----------+

Given the Employee table, write a SQL query that finds out employees who earn more than their managers. For the above table, Joe is the only employee who earns more than his manager.

+----------+
| Employee |
+----------+
| Joe |
+----------+

题意：

给定上述的一个数据表，要求写一个SQL的查询语句，找出那些赚得比他们的经理工资要多的员工的姓名。

题解：

此题考虑用连接来做。可以将一张表格考虑成两张表格来做，然后用内连接的不等值连接来取得相应的结果；这里有一个需要注意的地方：在输出的时候，需要将姓名的列名改为Employee。

select e.Name as Employee from Employee as e join Employee as x on e.ManagerId = x.Id and e.Salary >= x.Salary;

还有一种是用自连接来做：

select e.name as 'Employee'
        from Employee e,Employee m 
            where e.managerid=m.id 
                and
                   e.salary>m.salary;