Chapter-8 Database Concepts — Online MCQ Test
COMPUTER SCIENCE · CLASS 12 SECOND PUC · Karnataka State Board
Practice Chapter-8 Database Concepts with a free chapter-wise online MCQ test.
This chapter covers: relational model - primary key - candidate key - foreign key - attributes - tuples - cardinality - degree.
AI-generated questions from basic to board-exam level, with instant results and explanations.
Chapter-8 Database Concepts — Important Questions & Answers
What is a relation in the relational model?
- A. A mathematical concept represented as a table with rows and columns
- B. A connection between two databases
- C. A type of primary key constraint
- D. A method of organizing files sequentially
Answer: A. A mathematical concept represented as a table with rows and columns
In the relational model, a relation is a table consisting of rows (tuples) and columns (attributes) that represent data.
In the relational model, a relation is a table consisting of rows (tuples) and columns (attributes) that represent data.
Which of the following is the definition of a tuple?
- A. A column in a relational table
- B. A row in a relational table
- C. A data type used in databases
- D. A constraint applied to attributes
Answer: B. A row in a relational table
A tuple is a single row in a relational table that contains a set of attribute values.
A tuple is a single row in a relational table that contains a set of attribute values.
In a Student table with columns (StudentID, Name, Email, Phone), what is the degree of this relation?
- A. 1
- B. 2
- C. 3
- D. 4
Answer: D. 4
The degree is the number of attributes (columns), which are StudentID, Name, Email, and Phone = 4 attributes.
The degree is the number of attributes (columns), which are StudentID, Name, Email, and Phone = 4 attributes.
Analyze this situation: Table Course has CourseID as primary key. Table Enrollment has StudentID, CourseID. CourseID in Enrollment is marked as foreign key. What constraint is being enforced?
- A. Entity integrity only
- B. Referential integrity only
- C. Both entity and referential integrity
- D. Domain integrity only
Answer: B. Referential integrity only
The foreign key CourseID enforces referential integrity by ensuring every CourseID in Enrollment exists in the Course table's primary key.
The foreign key CourseID enforces referential integrity by ensuring every CourseID in Enrollment exists in the Course table's primary key.
[TRICKY] In a table with attributes (EmployeeID, Email, PhoneNumber), if Email is NULL for some records and PhoneNumber for others, but EmployeeID is always non-NULL and unique, then:
- A. Email or PhoneNumber could individually serve as a primary key
- B. Only EmployeeID can be a primary key due to NULL values in other attributes
- C. A composite key of (Email, PhoneNumber) is better than EmployeeID alone
- D. No primary key can be established for this table
Answer: B. Only EmployeeID can be a primary key due to NULL values in other attributes
Primary keys cannot contain NULL values; therefore, only EmployeeID with guaranteed uniqueness and non-NULL values can be the primary key.
Primary keys cannot contain NULL values; therefore, only EmployeeID with guaranteed uniqueness and non-NULL values can be the primary key.