【思路一】
select avg(salary) as avg_salary from salaries where to_date = '9999-01-01' and salary not in (select max(salary) from salaries where to_date='9999-01-01') and salary not in (select min(salary) from salaries where to_date='9999-01-01')
【思路二】
SELECT (SUM(salary) - MAX(salary) - MIN(salary)) / (COUNT(salary)-2) as avg_salary
FROM salaries where to_date = '9999-01-01';