nstructions

In our example instance of the instructor table $($tuple$),$ no two instructors have the same name. From this, can we conclude that name can be used as a superkey $($or primary key$)$ of instructor?

Consider the employee database below. What are the appropriate primary keys?

employee$($person$\_$name, street, city$)$

works$($person$\_$name, company$\_$name, salary$)$

company$($company$\_$name, city$)$

Consider the same employee database above. Give an expression in the relational algebra to express each of the following queries:

Find the name of each employee who lives in city $$Miami$.$

Find the name of each employee whose salary is greater than $$100000.$

Find the name of each employee who lives in $$Miami$$ and whose salary is greater than $$100000.$