题解 | 平均工资

# 找出在职员工的工资最大，最小值对应的员工
# 找出不是这种工资的员工，求平均
select
    avg(salary)
from
    salaries
where
    to_date = '9999-01-01' 
and 
    salary != (select max(salary) from salaries where to_date = '9999-01-01')
and 
    salary != (select min(salary) from salaries where to_date = '9999-01-01')