题解 | #获取当前薪水第二多的员工的emp_no以及其对应的薪水salary#

薪资第一和第二都可能有多名，所以需要group by

SELECT emp_no,salary FROM salaries s 
WHERE salary=
  (
    SELECT salary FROM salaries GROUP BY salary
    ORDER BY salary DESC LIMIT 1,1
  );