最简单解法 | 求薪水排名第二的员工，不用order by

核心思路：分别求两次maxSalary，第二次maxSalary如果小于第一次的maxSalary，那么它就是排名第二的薪资。

-- 第一次求maxSalary
select
    max(salary) as maxSalary
from salaries;

-- 第二次求maxSalary，同时判断是否小于第一次的maxSalary
-- 小于就证明是排名第二的薪资
select
    max(salary)
from salaries
where salary < ( select max(salary) as maxSalary from salaries));

-- 根据以上结果，查询薪资第二的员工信息
select
    t1.emp_no,
    salary,
    last_name,
    first_name
from employees t1
join salaries t2
on t1.emp_no = t2.emp_no
and salary = (
select max(salary) from salaries
where salary < (
select max(salary) as maxSalary
from salaries));