题解 | 查找在职员工自入职以来的薪水涨幅情况

SELECT 
    s_current.emp_no,
    (s_current.salary - s_start.salary) AS growth
FROM 
    (SELECT emp_no, salary 
     FROM salaries 
     WHERE to_date = '9999-01-01') s_current 
JOIN 
    (SELECT emp_no, salary 
     FROM salaries 
     WHERE from_date = (
         SELECT MIN(from_date) 
         FROM salaries s2 
         WHERE s2.emp_no = salaries.emp_no
     )) s_start  
    ON s_current.emp_no = s_start.emp_no
ORDER BY growth;