题解 | #统计出当前各个title类型对应的员工当前薪水对应的平均工资#

解题思路
1.联结两表，查询平均工资，按t.title分组，avg(s.salary)升序排序

SELECT t.title,avg(s.salary)
FROM titles AS t
INNER JOIN salaries AS s
ON t.emp_no=s.emp_no
WHERE t.to_date='9999-01-01'
AND s.to_date='9999-01-01'
GROUP BY t.title
ORDER BY avg(s.salary);