1. A relation in a database is also called a ______.
A. Column
B. Table
C. Row
D. Attribute
Answer: B
Explanation: In relational model, a relation corresponds to a table.
2. A row in a table is known as a ______.
A. Attribute
B. Tuple
C. Domain
D. Degree
Answer: B
Explanation: Tuple represents a single row of data.
3. The number of attributes in a relation is called its ______.
A. Cardinality
B. Degree
C. Tuple count
D. Domain
Answer: B
Explanation: Degree = number of columns in a table.
4. The number of rows in a relation is called its ______.
A. Degree
B. Domain
C. Cardinality
D. Schema
Answer: C
Explanation: Cardinality = number of tuples.
5. The set of permitted values for an attribute is its ______.
A. Domain
B. Range
C. Tuple
D. Key
Answer: A
Explanation: Domain defines valid data for an attribute.
6. Schema represents the ______ of the database.
A. Operational state
B. Current data
C. Logical structure
D. Physical storage
Answer: C
Explanation: Schema describes the blueprint of the database.
7. Which key uniquely identifies each record in a table?
A. Candidate key
B. Primary key
C. Super key
D. Alternate key
Answer: B
Explanation: Primary key is chosen candidate key for unique identification.
8. A minimal super key is called ______.
A. Composite key
B. Candidate key
C. Foreign key
D. Alternate key
Answer: B
Explanation: Candidate key is minimal set of attributes for uniqueness.
9. A foreign key ensures ______.
A. Data redundancy
B. Referential integrity
C. Data independence
D. Backup
Answer: B
Explanation: Foreign key maintains valid references between tables.
10. A key containing more than one attribute is called ______.
A. Composite key
B. Alternate key
C. Super key
D. Foreign key
Answer: A
Explanation: Composite key uses multiple columns for uniqueness.
11. A super key is a set of attributes that ______.
A. May or may not be unique
B. Uniquely identifies tuples
C. Contains only one attribute
D. Must be foreign keys
Answer: B
Explanation: Super keys guarantee uniqueness in a relation.
12. An alternate key is ______.
A. A primary key
B. A key not chosen as primary
C. Same as composite key
D. A foreign key
Answer: B
Explanation: Alternate keys are remaining candidate keys.
13. Null values indicate ______.
A. Zero
B. No value / Unknown
C. Negative value
D. Constraint violation
Answer: B
Explanation: Null means missing, not zero or empty.
14. Which integrity constraint ensures each tuple is unique?
A. Entity integrity
B. Domain integrity
C. Referential integrity
D. Key integrity
Answer: A
Explanation: Entity integrity requires primary key to be unique and not null.
15. Referential integrity is violated when ______.
A. A primary key is NULL
B. A foreign key references a non-existent primary key
C. Duplicate primary keys exist
D. A domain is missing
Answer: B
Explanation: Foreign keys must match valid primary keys.
16. Which is NOT allowed in a primary key?
A. Unique values
B. Null values
C. Composite attributes
D. Integer type
Answer: B
Explanation: Primary key cannot be NULL.
17. A relation is a ______.
A. Multi-dimensional array
B. Set of tuples
C. Linked list
D. Stack
Answer: B
Explanation: A relation is a mathematical set of tuples.
18. Two relations are union-compatible if ______.
A. They have same number of rows
B. They have same degree and matching domains
C. They reference same primary key
D. They store similar data
Answer: B
Explanation: Union requires same structure (degree + domain).
19. Which operation extracts columns?
A. Selection
B. Projection
C. Join
D. Union
Answer: B
Explanation: Projection chooses specific attributes (columns).
20. Which operation extracts rows?
A. Selection
B. Projection
C. Intersection
D. Cartesian product
Answer: A
Explanation: Selection filters tuples based on conditions.
21. Cartesian product results in ______.
A. Only matched rows
B. Only unmatched rows
C. All possible combinations
D. No output
Answer: C
Explanation: It combines every row of one table with every row of another.
22. The natural join removes ______.
A. All duplicate rows
B. Duplicate columns
C. Primary keys
D. Constraints
Answer: B
Explanation: Natural join merges equal columns, removing duplicates.
23. A relation must have all values atomic to be in ______.
A. 1NF
B. 2NF
C. 3NF
D. BCNF
Answer: A
Explanation: 1NF requires no multi-valued attributes.
24. In relational algebra, σ represents ______.
A. Join
B. Projection
C. Selection
D. Union
Answer: C
Explanation: Sigma (σ) is the selection operator.
25. In relational algebra, π represents ______.
A. Cartesion Product
B. Projection
C. Rename
D. Intersection
Answer: B
Explanation: Pi (π) selects specific columns.