题解 | #查找排除当前最大、最小salary之后的员工的平均工资avg_salary#

本题的两个需要注意点的
1.当前最大、最小 salary，则必须有条件to_date='9999-01-01';
2.先求出 max(salary)、min(salary);
2.排除最大、最小，则 where 条件为 salary 不在 max(salary),min(salary) 中，还要再加一个 to_date='9999-01-01'

select avg(salary) as avg_salary
from salaries
where salary not in ((select max(salary) 
                      from salaries
                      where to_date='9999-01-01'),
                     (select min(salary) 
                      from salaries
                      where to_date='9999-01-01'))
and to_date='9999-01-01'