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Test: Functional Dependency - Computer Science Engineering (CSE) MCQ


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10 Questions MCQ Test Question Bank for GATE Computer Science Engineering - Test: Functional Dependency

Test: Functional Dependency for Computer Science Engineering (CSE) 2024 is part of Question Bank for GATE Computer Science Engineering preparation. The Test: Functional Dependency questions and answers have been prepared according to the Computer Science Engineering (CSE) exam syllabus.The Test: Functional Dependency MCQs are made for Computer Science Engineering (CSE) 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Functional Dependency below.
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Test: Functional Dependency - Question 1

We can use the following three rules to find logically implied functional dependencies. This collection of rules is called

Detailed Solution for Test: Functional Dependency - Question 1

By applying these rules repeatedly, we can find all of F+, given F.

Test: Functional Dependency - Question 2

The relation employee(ID,name,street,Credit,street,city,salary) is decomposed into
employee1 (ID, name)
employee2 (name, street, city, salary)
This type of decomposition is called

Detailed Solution for Test: Functional Dependency - Question 2

Lossy-join decomposition is the decomposition used here.

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Test: Functional Dependency - Question 3

There are two functional dependencies with the same set of attributes on the left side of the arrow:
A->BC
A->B
This can be combined as

Detailed Solution for Test: Functional Dependency - Question 3

This can be computed as the canonical cover.

Test: Functional Dependency - Question 4

Suppose we wish to find the ID’s of the employees that are managed by people who are managed by the employee with ID 123. Here are two possible queries:
I. SELECT ee.empID
FROM Emps ee, Emps ff
WHERE ee.mgrID = ff.empID AND ff.mgrID = 123;
II. SELECT empID
FROM Emps 
WHERE mgrID IN
(SELECT empID FROM Emps WHERE mgrID = 123);
Which, if any, of the two queries above will correctly (in SQL2) get the desired set of employee ID’s?

Detailed Solution for Test: Functional Dependency - Question 4

The query can be satisfied by any of the two options.

Test: Functional Dependency - Question 5

Suppose now that R(A,B) and S(A,B) are two relations with r and s tuples, respectively (again, not necessarily distinct). If m is the number of (not necessarily distinct) tuples in the result of the SQL query:
R intersect S;
Then which of the following is the most restrictive, correct condition on the value of m?

Detailed Solution for Test: Functional Dependency - Question 5

The value of m must lie between the min value of r and s and 0.

Test: Functional Dependency - Question 6

Consider the following statements of RDBMS. Which of the following are correct?
I. Every relation in 3NF is also in BCNF
II. Every relation in BCNF is also in 3NF

Detailed Solution for Test: Functional Dependency - Question 6

Boyce-Codd Normal Form should satisfy the following two conditions:

  • It should be in the Third Normal Form.
  • And, for any dependency A → B, A should be a super key.

Relationship between 1NF, 2NF, 3NF and BCNF:

I. Every relation in 3NF is also in BCNF
False, Every relation in BCNF is also in 3NF. A relation schema that is in the third normal form then that table may or may not be in BCNF. Here 3NF is a subset of BCNF hence the given statement is False.
II. Every relation in BCNF is also in 3NF
True, Every relation in BCNF is also in 3NF. Here BCNF is a superset of 3NF hence the given statement is True.
Hence the correct answer is Only II is correct.

Test: Functional Dependency - Question 7

Consider the relation R(X, Y, Z, W, V) in which X, Y, Z, W, and V are the attributes and the following set of functional dependencies
A = {{X, Y} → {Z, W},  {X, W, V} → {Y, Z}}
Which of the following is the trivial functional dependency in A+, where A+ is closure of A?

Detailed Solution for Test: Functional Dependency - Question 7

Concept:
The closure of F, denoted as F+, is the set of all regular FD, that can be derived from.
For trivial functional dependency,
Let A and be two sets consists of attributes of a relation
A → B
A ⊇ B 
Option 1: 
{X, Z} → {Z, W}
{X, Z}  ⊉ {Z, W}
Not a trivial functional dependency

Option 2: 
{X, V} → {V}
{X, V} ⊇ {V}
It is a trivial functional dependency

Option 3: 
{X, W, V} → {Y}
{X, W, V} ⊉  {Y}
Not a trivial functional dependency

Option 4: 
{Y, W} → {Y, X}
{Y, W} ⊉ {Y, X}
Not a trivial functional dependency
NOTE:
⊇ → superset
⊉ → not superset

Test: Functional Dependency - Question 8

Consider a relational schema S = (U, V, W, X, Y, Z) on which the following functional dependencies hold:
{U → V, VW → X, Y → W, X → U}
Which are the candidate keys among following options?

Detailed Solution for Test: Functional Dependency - Question 8

Concept:
A candidate key is a column, or set of columns, in a table that can uniquely identify any database record without referring to any other data
The following functional dependencies,
U → V, VW → X, Y → W, X → U
S = (U, V, W, X, Y, Z)
Here YZ is an independent key. So, for every key, the YZ should their. Hence only option 4 is containing YZ for all keys.
∴ Hence the correct answer is UYZ, VYZ, XYZ.

Test: Functional Dependency - Question 9

A relation in which every non-key attribute is fully functionally dependent on the primary key and which has no transitive dependencies is in -

Detailed Solution for Test: Functional Dependency - Question 9

1NF:

  • There are only Single Valued Attributes.
  • There is a unique name for every Attribute/Column.

2NF:

  • A relation that is in First Normal Form 
  • Every non-primary-key attribute is fully functionally dependent on the primary key 

3NF

  • The third normal form is based on the concept of transitive dependency. A functional dependency X->Y in a relation schema R is a transitive dependency if there exists a set of attributed Z in R that is neither a candidate key nor a subset of any key of R.
  • A relation is in 3NF if it satisfies 2NF and no prime attribute of R is transitively dependent on the primary key.
  • If X - > A is a functional dependency, then A should be a prime attribute or X should be a candidate key.
  • Lossless join and dependency preservation is always possible in 3NF. 3NF decomposition is always lossless join and dependency preserving.

BCNF:

  • It stands for Boyce Codd normal form.
  • A relation R is in BCNF if whenever a non-trivial functional dependency X -> A holds in R, then X is a superkey of R. Any relation with two attributes is always in BCNF. Because when a relation contains only two attributes then one attribute determines another and the left side of the functional dependency will always be a candidate key in that case.
  • BCNF is not always dependency preserving.

Therefore the answer is Option 1.

Test: Functional Dependency - Question 10

Which of the following is not Armstrong’s Axiom?

Detailed Solution for Test: Functional Dependency - Question 10

It is possible to use Armstrong’s axioms to prove that Pseudotransitivity rule is sound.

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