题解 | 似乎一张表就可以，用CONCAT
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 d.dept_no, d.emp_no, s.salary as maxSalary FROM dept_emp d JOIN salaries s ON d.emp_no = s.emp_no WHERE CONCAT(d.dept_no, s.salary) IN (SELECT CONCAT(d.dept_no, MAX(s.salary)) FROM dept_emp d JOIN salaries s ON d.emp_no = s.emp_no GROUP BY d.dept_no) ORDER BY dept_no