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Module 3 Final Quiz: Relational Model & Keys MCQs
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1
In the formal Relational Model (E.F. Codd), what are the formal terms for Table, Row, and Column?
A.
Table = File, Row = Record, Column = Field
B.
Table = Relation, Row = Tuple, Column = Attribute
C.
Table = Schema, Row = Object, Column = Member
D.
Table = Domain, Row = Instance, Column = Type
Explanation & Key
Correct Answer:
2
What is the Degree and Cardinality of a relation?
A.
Degree = Number of rows; Cardinality = Number of columns
B.
Degree = Number of attributes (columns); Cardinality = Number of tuples (rows)
C.
Degree = Index depth; Cardinality = Table file size
D.
Degree = Foreign keys count; Cardinality = Primary key size
Explanation & Key
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3
What is a Super Key in relational database theory?
A.
A key that contains all columns of a table
B.
Any set of one or more attributes that uniquely identifies a tuple within a relation (may contain superfluous/redundant attributes)
C.
A primary key encrypted with RSA
D.
A key that links to another database server
Explanation & Key
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4
What is the precise definition of a Candidate Key?
A.
A key chosen by users during an election
B.
A minimal Super Key (a super key from which no attribute can be removed without destroying uniqueness)
C.
A key that can accept NULL values
D.
A foreign key that points to itself
Explanation & Key
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5
What two strict integrity rules MUST a Primary Key satisfy?
A.
It must be an integer and greater than 0
B.
It must be strictly UNIQUE across all rows, and NOT NULL (Entity Integrity Constraint)
C.
It must be encrypted and contain letters
D.
It must be indexed as a B-tree and foreign key
Explanation & Key
Correct Answer:
6
What is an Alternate Key?
A.
A backup database server
B.
Any Candidate Key that was NOT selected by the database designer to be the Primary Key
C.
A foreign key pointing to a composite key
D.
A key that alternates between even and odd values
Explanation & Key
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7
What is the Referential Integrity Constraint enforced by Foreign Keys?
A.
A foreign key must always be an integer
B.
A foreign key value in a referencing table must either match a valid primary key value in the referenced table, or be NULL
C.
A table cannot have more than one foreign key
D.
Foreign keys must have the exact same column name as the referenced primary key
Explanation & Key
Correct Answer:
8
What happens when a row in a parent table is deleted with foreign key constraint ON DELETE CASCADE?
A.
The deletion is blocked and throws an error
B.
All referencing child rows in the child table are automatically deleted as well
C.
The child table is dropped from the database
D.
The child row foreign keys are set to NULL
Explanation & Key
Correct Answer:
9
In Relational Algebra, what does the Selection operator ($sigma_{condition}$) do?
A.
Selects columns to display in output
B.
Filters horizontal tuples (rows) that satisfy a specified predicate condition (equivalent to SQL WHERE)
C.
Performs a cartesian join of two relations
D.
Orders rows alphabetically
Explanation & Key
Correct Answer:
10
In Relational Algebra, what does the Projection operator ($pi_{attributes}$) do?
A.
Filters rows based on values
B.
Selects specific vertical columns (attributes) from a relation and removes duplicate tuples
C.
Creates a foreign key constraint
D.
Calculates mathematical sums
Explanation & Key
Correct Answer:
11
If relation $R$ has 5 tuples and relation $S$ has 10 tuples, how many tuples are in their Cartesian Product ($R imes S$)?
A.
15 tuples
B.
50 tuples ($5 imes 10$)
C.
2 tuples
D.
0 tuples
Explanation & Key
Correct Answer:
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