Database Design(Normal Forms)

Question 81

Suppose the following functional dependencies hold on a relation U with attributes P,Q,R,S, and T:

P → QR
RS → T 

Which of the following functional dependencies can be inferred from the above functional dependencies?

• PS → T
• R → T
• P → R
• PS → Q

Question 82

Relation R has eight attributes ABCDEFGH. Fields of R contain only atomic values. F = {CH -> G, A -> BC, B -> CFH, E -> A, F -> EG} is a set of functional dependencies (FDs) so that F+ is exactly the set of FDs that hold for R. How many candidate keys does the relation R have?

• 3
• 4
• 5
• 6

Question 83

In RDBMS, different classes of relations are created using __________ technique to prevent modification anomalies.

• Functional Dependencies
• Data integrity
• Referential integrity
• Normal Forms

Question 84

A relation r(A,B) in a relational database has 1200 tuples. The attribute A has integer values ranging from 6 to 20, and the attribute B has integer values ranging from 1 to 20. Assume that the attributes A and B are independently distributed. The estimated number of tuples in the output of σ_{(A>10)∨(B=18)}(r) is ____________.

• 820
• 1200
• 960
• 1000

Question 85

Relations produced from E - R Model will always be in ________.

• 1 NF
• 2 NF
• 3 NF
• 4 NF

Question 86

Consider the relation R (ABCDE): FD = { A → B, B → C, C → D, D → E} Find out the highest normal form.

• 1 NF
• 2 NF
• 3 NF
• BCNF

Question 87

Let R = ABCDE is a relational scheme with functional dependency set F = {A → B, B → C, AC → D}. The attribute closures of A and E are

• ABCD, φ
• ABCD, E
• Φ, φ
• ABC, E

Question 88

BCNF is not used for cases where a relation has

• Two (or more) candidate keys
• Two candidate keys and composite
• The candidate key overlap
• Two mutually exclusive foreign keys

Question 89

The Relation Vendor Order (V_no, V_ord_no, V_name, Qty_sup, unit_price) is in 2NF because:

• Non_key attribute V_name is dependent on V_no which is part of composite key
• Non_key attribute V_name is dependent on Qty_sup
• Key attribute Qty_sup is dependent on primary_key unit price
• Key attribute V_ord_no is dependent on primary_key unit price