题解 | 在子查询中使用窗口函数，计算每组工资排序rk
获取每个部门中当前员工薪水最高的相关信息
https://www.nowcoder.com/practice/4a052e3e1df5435880d4353eb18a91c6
SELECT
dept_no,
emp_no,
salary AS maxSalary
FROM(
SELECT
de.emp_no, de.dept_no, s.salary,
RANK() OVER(PARTITION BY dept_no ORDER BY salary DESC) AS rk
FROM dept_emp de
JOIN salaries s USING(emp_no)
) t1
WHERE rk=1
ORDER BY dept_no
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