DBI202_PART2

QN=17 (6831) What is a primary key?

• a. A primary key is the field(s) in a table that uniquely defines that table in a database

• b. A primary key is the field(s) in a table that is used to establishes a relationship between two tables

• c. A primary key is the field(s) in a table that uniquely defines the row in the table

• d. A primary key is the field(s) in a table that is used to establishes a relationship between two databases

QN=19 (6822) Which statement is used to add a column named D into the relation R?

• a. ALTER TABLE R ADD D [DataType];

• b. ALTER TABLE R ADD ATTRIBUTE D [DataType];

• c. ALTER TABLE R ADD PROPERTY D [DataType];

QN=20 (6821) Which one of the following is NOT a DML command?

• a. DELETE

• b. GRANT

• c. INSERT

• d. UPDATE

QN=22 (6811) The relational operator that adds all possible pairs of rows from two tables is known as the .... operator.

• a. union

• b. product

• c. join

• d. selection

QN=23 (7956) Let R(ABCDEFGH) satisfies the following functional dependencies:
A -> B,
CH -> A,
B -> E,
BD -> C,
EG -> H,
DE -> F.
Which of the following FDs is also guaranteed to be satisfied by R?

• a. CGH -> BF

• b. ACG -> DH

• c. ADG -> CH

• d. BCD -> FH

QN=25 (7969) Consider a relation with schema R(A, B, C, D) and FD's BC -> D, D -> A, A -> B. Which of the following is the key of R?

• a. BD

• b. BC

• c. D

• d. AB

QN=26 (7963) Given the relation schema R(A,B,C) and functional dependencies
F = {AB-> C, B->A, C->B}.
Which attribute(s) is/are prime?

• a. only A

• b. only B

• c. A and B

• d. B and C

QN=27 (7971) Given the relation R(ABCDE) with the following FD's:
D -> C,
CE ->A,
D ->A, and
AE ->D
Which of the following attribute set is a key?

• a. ABCDE

• b. CDE

• c. ABE

• d. BD

QN=29 (7967) A set of attributes forms a ____ for a relation if we do not allow 2-tuples in a relation instance to have the same values in all that attributes

• a. Key

• b. Foreign Key

• c. Index Key

• d. Trigger Key

QN=32 (7981) Suppose we have a relation R(ABCD) with FD's:
BC -> A ;
AD -> C ;
CD -> B ;
BD -> C

• a. R is in BCNF

• b. R is not in BCNF

• c. All of the others

• d. None of the others