自连接的代码是不是有误，日期判断应该写在where里，而且没有输出编号 我的更改 WITH second_highest_salary AS ( SELECT s1.salary FROM salaries s1 JOIN salaries s2 ON s1.salary < s2.salary WHERE s1.to_date = '9999-01-01' AND s2.to_date = '9999-01-01' GROUP BY s1.salary HAVING COUNT(DISTINCT s2.salary) = 1 ) SELECT emp_no, salary FROM salaries WHERE to_date = '9999-01-01' AND salary = (SELECT salary FROM second_highest_salary);