题解 | #获取所有员工当前的manager#
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
http://www.nowcoder.com/practice/c8652e9e5a354b879e2a244200f1eaae
select t.title,avg(s.salary) as av from titles as t,salaries as s where t.emp_no = s.emp_no group by t.title order by av asc