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

1--
select emp_no ,salary from salaries where to_date = '9999-01-01' and salary =
(select salary from salaries where to_date = '9999-01-01'  group by salary order by salary desc limit 1,1)
order by emp_no
2--
select emp_no,salary from(
select emp_no, salary,dense_rank()over(order by salary desc)rk from salaries where to_date='9999-01-01') e
where e.rk=2
order by emp_no
第一思路窗口函数，直接排名，必须用dense_rank应对多个相同薪水的情况
第二思路用分组group by，直接对salary去重了，通过limit获取第二多，需注意内外都需对时间过滤