题解 | #查找在职员工自入职以来的薪水涨幅情况#

先找出员工刚入职时候的工资 ， 利用入职时间连表查询

找出员工现在的工资

将1. 2.得出的子表 进行连表查询

SELECT 
 s1.emp_no,
 s1.salary - s2.salary growth
FROM
  (    
     SELECT 
         emp_no,
         salary
     FROM salaries 
     WHERE to_date = '9999-01-01'
   ) s1
   JOIN
   (SELECT
     e.emp_no,
     s.salary
     FROM
     employees e JOIN salaries s ON
     e.emp_no = s.emp_no
     WHERE e.hire_date = s.from_date
   ) s2
   on s1.emp_no = s2.emp_no
   ORDER BY growth ASC;