Exercise 20.7 Consider the following BCNF relations, which describe departments in a company and employees:
Dept(did, dname, location, managerid) Emp(eid, sal)
You are told that the following queries are extremely important:
■ List the names and ids of managers for each department in a user-specified location, in alphabetical order by department name.
■ Find the average salary of employees who manage departments in a user-specified location. You can assume that no one manages more than one department.
1. Describe the file structures and indexes that you would choose.
2. You subsequently realize that updates to these relations are frequent. Because indexes incur a high overhead, can you think of a way to improve performance on these queries without using indexes?
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