with employed as (
    select *
    from 
        salaries
    where 
        to_date = '9999-01-01'
),

salary_bound as (
    select
        max(salary) as max_salary,
        min(salary) as min_salary
    from 
        employed
)

select 
    round(avg(salary),3) as avg_salary
from    
    employed,salary_bound as b
where 
    salary < b.max_salary and salary > b.min_salary