题解 | #查找employees表emp_no与last_name的员工信息#
查找在职员工自入职以来的薪水涨幅情况
http://www.nowcoder.com/practice/fc7344ece7294b9e98401826b94c6ea5
1.先查询员工入职工资
（select e.emp_no, s.salary from employees e left join salaries s
on e.emp_no = s.emp_no where e.hire_date = s.from_date） a
2.查询在职员工工资（to_date='9999-01-01'时，表示依然在职）
(select s.emp_no, s.salary from salaries s where s.to_date = '9999-01-01') b
3.将以上a，b两表连接查询，计算growth（a.salary-b.salary），不排除降薪的可能
select a.emp_no, （a.salary-b.salary) as growth from
(select e.emp_no, s.salary from employees e left join salaries s on e.emp_no = s.emp_no where
e.hire_date = s.from_date) a join
(select s.emp_no, s.salary from salaries s where s.to_date = '9999-01-01') b on a.emp_no = b.emp_no
order by growth
