DBMS Notes
1. Which of the following is NOT a component of a DBMS? - A) Query Processor - B) Storage Manager - C) Compiler - D) Transaction Manager
Unit 1 — Introduction & ER Model
1. Which of the following is NOT a component of a DBMS?
- A) Query Processor
- B) Storage Manager
- C) Compiler
- D) Transaction Manager
Answer: C — A compiler is not a DBMS component. DBMS includes query processor, storage manager, and transaction manager.
3. Which key uniquely identifies each record in a table?
- A) Foreign Key
- B) Candidate Key
- C) Primary Key
- D) Super Key
Answer: C — Primary key uniquely identifies each row and cannot be NULL.
4. An ER diagram is used to represent:
- A) Physical storage of data
- B) Conceptual design of a database
- C) SQL queries
- D) Index structures
Answer: B — ER diagrams model the conceptual/logical design.
5. A weak entity set is one that:
- A) Has no attributes
- B) Cannot exist without a related strong entity
- C) Has multiple primary keys
- D) Contains only foreign keys
Answer: B — Weak entities depend on strong entities for identification.
6. In an ER diagram, a relationship between one entity from set A and many from set B is called:
- A) Many-to-Many
- B) One-to-One
- C) One-to-Many
- D) Many-to-One
Answer: C — One-to-Many (1:N) cardinality.
7. Data independence means:
- A) Data is stored independently on different servers
- B) Changes in one level do not affect other levels
- C) Each user has their own copy of data
- D) Data is not dependent on applications
Answer: B — Data independence allows schema changes at one level without affecting others.
8. Which data model uses tables to represent data?
- A) Hierarchical Model
- B) Network Model
- C) Relational Model
- D) Object-Oriented Model
Answer: C — The relational model uses tables (relations).
Unit 2 — Relational Model & SQL
9. The SELECT operation in relational algebra is equivalent to which SQL clause?
- A) SELECT
- B) FROM
- C) WHERE
- D) GROUP BY
Answer: C — The relational algebra SELECT filters rows, corresponding to the SQL WHERE clause.
10. Which SQL command is used to remove a table permanently?
- A) DELETE
- B) TRUNCATE
- C) DROP
- D) REMOVE
Answer: C — DROP TABLE removes the table structure and all data permanently.
11. A view in SQL is:
- A) A physical copy of a table
- B) A virtual table based on a query
- C) An index on a table
- D) A stored procedure
Answer: B — Views are virtual tables defined by a SELECT query.
12. Which join returns only matching rows from both tables?
- A) Left Join
- B) Right Join
- C) Full Outer Join
- D) Inner Join
Answer: D — INNER JOIN returns rows with matching values in both tables.
13. DCL stands for:
- A) Data Control Language
- B) Data Creation Language
- C) Database Command Language
- D) Data Check Language
Answer: A — DCL includes GRANT and REVOKE commands.
14. Which aggregate function returns the number of rows?
- A) SUM()
- B) AVG()
- C) COUNT()
- D) MAX()
Answer: C — COUNT() returns the number of rows matching a condition.
15. A trigger in SQL fires:
- A) Only when a SELECT is executed
- B) Automatically in response to DML events
- C) Only when called explicitly
- D) During database startup
Answer: B — Triggers execute automatically on INSERT, UPDATE, or DELETE events.
Unit 3 — Normalization
16. A relation is in 2NF if:
- A) It is in 1NF and has no partial dependencies
- B) It is in 1NF and has no transitive dependencies
- C) It has a composite primary key
- D) All attributes are multi-valued
Answer: A — 2NF eliminates partial functional dependencies on composite primary keys.
17. BCNF is a stricter version of:
- A) 1NF
- B) 2NF
- C) 3NF
- D) 4NF
Answer: C — BCNF (Boyce-Codd Normal Form) is a stricter version of 3NF.
18. Armstrong's axioms include:
- A) Reflexivity, Augmentation, Transitivity
- B) Union, Intersection, Difference
- C) Selection, Projection, Join
- D) Closure, Normalization, Decomposition
Answer: A — Reflexivity, Augmentation, and Transitivity are the three Armstrong axioms.
19. A lossless decomposition ensures:
- A) No data redundancy
- B) Original relation can be reconstructed via natural join
- C) All functional dependencies are preserved
- D) No null values exist
Answer: B — Lossless join decomposition allows reconstruction of the original relation.
20. Multivalued dependency is associated with:
- A) 3NF
- B) BCNF
- C) 4NF
- D) 5NF
Answer: C — 4NF eliminates non-trivial multivalued dependencies.
Unit 4 — Transactions & Concurrency
21. ACID properties stand for:
- A) Atomicity, Consistency, Isolation, Durability
- B) Accuracy, Completeness, Integrity, Dependency
- C) Association, Concurrency, Independence, Distribution
- D) Atomicity, Concurrency, Integrity, Distribution
Answer: A — ACID: Atomicity, Consistency, Isolation, Durability.
22. In two-phase locking, the two phases are:
- A) Read and Write
- B) Growing and Shrinking
- C) Lock and Unlock
- D) Begin and Commit
Answer: B — 2PL has a growing phase (acquiring locks) and a shrinking phase (releasing locks).
23. Which problem arises when two transactions wait for each other to release locks?
- A) Starvation
- B) Cascading Rollback
- C) Deadlock
- D) Dirty Read
Answer: C — Deadlock occurs when transactions form a circular wait for resources.
24. A dirty read occurs when:
- A) A transaction reads committed data
- B) A transaction reads data written by an uncommitted transaction
- C) Two transactions read the same row
- D) A transaction reads null values
Answer: B — Dirty read: reading uncommitted (potentially rolled-back) data.
25. Which recovery technique uses a log to undo incomplete transactions?
- A) Shadow Paging
- B) Checkpointing
- C) Log-Based Recovery
- D) ARIES
Answer: C — Log-based recovery uses write-ahead logging to undo/redo transactions.
Unit 5 — Storage & Indexing
26. A B+ tree differs from a B-tree in that:
- A) B+ tree stores data only in leaf nodes
- B) B+ tree has fewer levels
- C) B+ tree does not support range queries
- D) B+ tree uses hashing
Answer: A — B+ tree stores all data records in leaf nodes; internal nodes store only keys.
27. Which indexing type uses a hash function to locate records?
- A) Dense Index
- B) Sparse Index
- C) Hash Index
- D) Clustered Index
Answer: C — Hash indexing computes bucket addresses using a hash function.
28. Query optimization aims to:
- A) Maximize storage usage
- B) Find the most efficient query execution plan
- C) Eliminate SQL syntax errors
- D) Reduce the number of tables
Answer: B — Query optimization selects the lowest-cost execution plan.
Unit 6 — Advanced Topics
29. In a distributed database, fragmentation refers to:
- A) Data corruption across nodes
- B) Dividing data across multiple sites
- C) Replicating data to multiple servers
- D) Breaking indexes into smaller pieces
Answer: B — Fragmentation divides relations into horizontal or vertical fragments stored at different sites.
30. NoSQL databases are characterized by:
- A) Fixed schema and ACID compliance only
- B) Schema flexibility and horizontal scalability
- C) Support for joins only
- D) Single-server architecture
Answer: B — NoSQL databases offer flexible schemas and horizontal scaling for large datasets.
Answer Key Summary
| Q | A | Q | A | Q | A |
|---|---|---|---|---|---|
| 1 | C | 11 | B | 21 | A |
| 2 | B | 12 | D | 22 | B |
| 3 | C | 13 | A | 23 | C |
| 4 | B | 14 | C | 24 | B |
| 5 | B | 15 | B | 25 | C |
| 6 | C | 16 | A | 26 | A |
| 7 | B | 17 | C | 27 | C |
| 8 | C | 18 | A | 28 | B |
| 9 | C | 19 | B | 29 | B |
| 10 | C | 20 | C | 30 | B |
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