SQL Test 01

Given the following SQL Server db schema

Provide a sql file with the answers to the following questions:

1. Select employees that don't have a boss in the same department?
2. Select all departments along with the total salary there
3. Select departments that have less than 3 people in it
4. Select all departments along with the number of people there
5. Select employees who have the biggest salary in their departments
6. Select employees (names only) who have a bigger salary than their boss

Bonus

1. Provide a stored procedure including all of the answers above
2. Respond to the following question: your select query has over 50 joins and is painfully slow. Which steps would you take to speed its execution? You cannot create indexes, as this is a DBA task, and we assume they have been created correctly