请你查找薪水排名第二多的员工信息，不用order by

正确做法：

#select max(salary) from salaries;#先找薪水第一多

#select max(salary) from salaries
#where salary<(select max(salary) from salaries);#再找第二多

#最后找薪水等于第二多的。
select e.emp_no,salary,last_name,first_name
from employees as e
join salaries as s
on e.emp_no = s.emp_no
where salary=(select max(salary) from salaries
              where salary<(select max(salary) from salaries));

错误做法：
无group by,但select中包含聚合函数以及其他字段，那么返回的字段值与聚合函数并非一一对应的。

select e.emp_no,max(salary) as salary,last_name,first_name
from employees as e
join salaries as s
on e.emp_no=s.emp_no
where salary<(select max(salary)
              from employees e join salaries s on e.emp_no=s.emp_no);

返回结果：emp_no=10002，salary=74057,员工编号并不是薪水第二大的10004。