思路:查找一个数,在salary里面只有一个数大于它,那么它就是第二大的数。 # 找出一个只存在一个数大于其的数 SELECT em.emp_no,s.salary,em.last_name,em.first_name FROM employees em NATURAL JOIN salaries s WHERE EXISTS (SELECT * FROM salaries s1 GROUP BY (s1.salary>s.salary) # 以s.salary为界分组 HAVING s1.salary>s.salary AND COUNT(DISTINCT s1.salary)=...