BCS Database Management Systems 1 — Questions and Answers
Question 1: What does ACID stand for in database transactions?
- Atomicity, Consistency, Isolation, Durability (Correct answer)
- Accuracy, Completeness, Integrity, Dependability
- Atomicity, Completeness, Isolation, Distribution
- Access, Control, Integrity, Data
Correct answer: Atomicity, Consistency, Isolation, Durability
ACID stands for Atomicity (all-or-nothing), Consistency (valid state transitions), Isolation (concurrent transactions don't interfere), and Durability (committed data persists).
Question 2: What is a primary key in a relational database?
- The first column in a table
- A unique identifier for each row in a table that cannot be NULL (Correct answer)
- A foreign key reference to another table
- An index on the most frequently queried column
Correct answer: A unique identifier for each row in a table that cannot be NULL
A primary key is a column or set of columns that uniquely identifies each row in a table and cannot contain NULL values.
Question 3: Which SQL command is used to retrieve data from a database?
- INSERT
- UPDATE
- SELECT (Correct answer)
- DELETE
Correct answer: SELECT
The SELECT statement retrieves data from one or more tables, with optional filtering (WHERE), grouping (GROUP BY), and sorting (ORDER BY) clauses.
Question 4: What is the purpose of normalization in database design?
- To increase query execution speed
- To reduce data redundancy and improve data integrity (Correct answer)
- To encrypt sensitive data fields
- To partition data across multiple servers
Correct answer: To reduce data redundancy and improve data integrity
Database normalization organizes tables to minimize data redundancy and dependency by dividing large tables into smaller, logically related ones.
Question 5: What is a foreign key constraint?
- A key that locks a table from modifications
- A column that references the primary key of another table, enforcing referential integrity (Correct answer)
- An index on a non-primary column
- A key used for encryption
Correct answer: A column that references the primary key of another table, enforcing referential integrity
A foreign key is a column in one table that refers to the primary key in another table, ensuring referential integrity between related tables.
Question 6: Which normal form eliminates partial dependencies on composite primary keys?
- First Normal Form (1NF)
- Second Normal Form (2NF) (Correct answer)
- Third Normal Form (3NF)
- Boyce-Codd Normal Form (BCNF)
Correct answer: Second Normal Form (2NF)
2NF requires that the table is in 1NF and that every non-key attribute is fully functionally dependent on the entire composite primary key, not just part of it.
BCS Database Management Systems 1
What does ACID stand for in database transactions?