for the following BCNF relations that describe departments in a company and employees

Dept(did,dname,location,managerid) Emp(eid,sal)

Now for this system the following queries are important: List the names and ids of managers for each department in a user-specified location and in alphabetical order by department name. find the average salary of employees who manage departments in a user specified location. no one manages more than one department

Now what do you think is the best file structure and indexes to use? Now since i realised that updates will be very frequent indexes will prob have high overhead is there any other way other than using indexes to improve performance