获取薪水第二多的员工的emp_no及其对应的薪水salary

/*自链接，s1.salary<s2.salary 按照s1分组，s2计数有2个时，就是排名第二的薪资。
*/
with t as(
    select s1.salary
from salaries s1
join salaries s2 on s1.salary<=s2.salary
group by s1.salary having count(s2.salary)=2
)

select 
    emp_no,
    salary,
    last_name,
    first_name
from employees
left join salaries using(emp_no)
where salary in (select salary from t)