Oracle HR 模式。从员工中选择最高工资答案

【问题标题】：Oracle HR Schema. Selecting of max salary from EmployeesOracle HR 模式。从员工中选择最高工资
【发布时间】：2021-08-07 17:51:24
【问题描述】：

我需要从 Oracle HR Schema 中选择城市、城市的最高薪水和薪水最高的员工姓名。我尝试执行以下代码，但城市名称重复：

select l.city, e.last_name, e.salary from locations l 
inner join departments d on l.location_id = d.location_id
inner join employees e on d.department_id = e.department_id
and e.salary = (select max(salary) from employees where department_id = d.department_id)
group by l.city, e.last_name, e.salary
order by e.salary;

我的代码有什么问题？我已经附上了我需要的结果。Correct SQL result

【问题讨论】：

标签： oracle greatest-n-per-group

【解决方案1】：

您可以使用DENSE_RANK 分析函数（将返回每个城市最高工资的所有员工）：

SELECT city,
       last_name,
       salary
FROM   (
  SELECT l.city,
         e.last_name,
         e.salary,
         DENSE_RANK() OVER (
           PARTITION BY l.location_id
           ORDER BY e.salary DESC
         ) AS rnk
  FROM   locations l
         INNER JOIN departments d
         ON l.location_id = d.location_id
         INNER JOIN employees e
         ON d.department_id = e.department_id
)
WHERE  rnk = 1;

或与KEEP 聚合（这将只返回每个位置的最高薪水和最大姓氏的一名员工）：

SELECT MAX(l.city) AS city,
       MAX(e.last_name) KEEP ( DENSE_RANK LAST ORDER BY e.salary ) AS last_name,
       MAX(e.salary) AS salary
FROM   locations l
       INNER JOIN departments d
       ON l.location_id = d.location_id
       INNER JOIN employees e
       ON d.department_id = e.department_id
GROUP BY
       l.location_id

我的代码有什么问题？

您是在 department_id = d.department_id 上关联，而不是在位置（或城市名称；但是，不要聚合城市名称，因为可能有两个不同的位置同名）。

【讨论】：