查找排除当前最大、最小salary之后的员工的平均工资avg_salary

CREATE TABLE `salaries` ( `emp_no` int(11) NOT NULL,
`salary` int(11) NOT NULL,
`from_date` date NOT NULL,
`to_date` date NOT NULL,
PRIMARY KEY (`emp_no`,`from_date`));

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

select max(salary) from salaries where s.to_date = '9999-01-01')
select min(salary) from salaries where s.to_date = '9999-01-01')

select * from salaries where to_data = '9999-01-01' and salary not in maxRecord and salary not in minRecord

select avg(salary) from t1