DMDB 1

DMDB 1

Assessment

Quiz

Computers

9th - 12th Grade

Practice Problem

Easy

Created by

qzzxfns95h aus

Used 2+ times

FREE Resource

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14 questions

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1.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Keys enforce uniqueness

True

False

Answer explanation

This is true. A (Candidate) Key is a minimal set of fields that identify each tuple uniquely.

2.

FILL IN THE BLANK QUESTION

1 min • 1 pt

R1 ⋃ R2 defines the ... of relations R1 and R2

Answer explanation

Media Image

This describes the union of R1 and R2

3.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

Choose the correct relational algebra operator which corresponds to selection

σ

s

Π

ρ

Answer explanation

Media Image

σ (sigma) stands for selection. In Relational Algebra, selection returns tuples which satisfy a given condition

4.

MULTIPLE SELECT QUESTION

45 sec • 1 pt

Difference

Union

Answer explanation

Media Image

This is the definition of the difference

5.

FILL IN THE BLANK QUESTION

1 min • 1 pt

Π stands for...

Answer explanation

Media Image

Projection only keeps a subset of columns of some relation.

Hint to remember: Π represents "Pi" and Projection starts with P

6.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

The intersection in relational algebra can be defined only by the difference:

No

Answer explanation

Media Image

7.

MULTIPLE CHOICE QUESTION

30 sec • 1 pt

If A contains 2 tuples and B contains 4 tuples, then A X B contains ... tuples

2

4

8

6

Cannot be said, depends on A and B

Answer explanation

Media Image

Note that A and B are sets. The cartesian/cross product A X B contains |A| * |B| tuples (recall from discrete maths)

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