1. For each attribute of a relation, there is a set of permitted values, called the ________ of that attribute.

Answer. Domain

2. Database ____ which is the logical design of the database, and the database _ which is a snapshot of the data in the database at a given instant in time.

Answer. Schema, Instance

3. Which attribute can be taken as a primary key?

Answer. Id

4. The result which operation contains all pairs of tuples from the two relations, regardless of whether their attribute values match.

Answer. Cartesian product

5. The _______operation performs a set union of two "similarly structured" tables

Answer. Union

6. Which cannot be taken as a primary key?

Answer. Street

7. "Find all students who have taken all courses offered in the Biology department." The expressions that matches this sentence is :

Answer. _ t _ r (Q(t))

8. Which symbol is used as comparison operator in tuple relational calculus ?

Answer. =

9. The ___________ operation, denoted by _, allows us to find tuples that are in one relation but are not in another.

Answer. Set-difference

10. Which is a unary operation:

Answer. Generalized selection