# Important Viva Questions — DBMS ## Unit 1 — Introduction & ER Model 1. What is a DBMS? How is it different from a file system? 2. What are the four main characteristics of a database? 3. What is the three-level ANSI/SPARC architecture? 4. Define logical and physical data independence. 5. What is a schema? How does it differ from an instance? 6. What are the different types of database users? 7. What is the role of a Database Administrator (DBA)? 8. What are the main components of a DBMS? 9. Define an entity, attribute, and relationship in the ER model. 10. What is the difference between a simple and composite attribute? 11. What are the different types of keys in a database? 12. What is the difference between primary key and candidate key? 13. What is a foreign key? How does it enforce referential integrity? 14. What is cardinality? Explain the types with examples. 15. What is a weak entity? How is it represented in an ER diagram? 16. What is specialization? How is it different from generalization? 17. What is aggregation in an ER model? 18. What are the different data models? Compare hierarchical and relational models. --- ## Unit 2 — Relational Model & SQL 1. Define a relation, tuple, and attribute in the relational model. 2. What are the properties of a relational table? 3. What is relational algebra? Name its basic operations. 4. What is the difference between selection and projection in relational algebra? 5. What is a natural join? How does it differ from a theta join? 6. What is relational calculus? Differentiate TRC and DRC. 7. What is the difference between DDL, DML, DCL, and TCL? 8. What are integrity constraints in SQL? 9. What is the difference between DELETE, TRUNCATE, and DROP? 10. Explain the different types of SQL joins with examples. 11. What is a nested query (subquery)? When is it used? 12. What is a correlated subquery? 13. What is a view? What are its advantages and limitations? 14. What is a trigger? When does it fire? 15. What is the difference between a function and a stored procedure? 16. What is a cursor? When is it used in PL/SQL? --- ## Unit 3 — Normalization 1. What is normalization? Why is it needed? 2. What is a functional dependency? Give an example. 3. What is a partial functional dependency? 4. What is a transitive functional dependency? 5. State Armstrong's axioms and their names. 6. What is the closure of a set of attributes? 7. What is a canonical cover? 8. Define 1NF, 2NF, and 3NF with examples. 9. What is BCNF? How does it differ from 3NF? 10. When can a relation be in 3NF but not in BCNF? 11. What is a multivalued dependency? 12. What is 4NF? 13. What is 5NF (Project-Join Normal Form)? 14. What is lossless decomposition? How is it tested? 15. What is dependency preservation? --- ## Unit 4 — Transactions & Concurrency 1. What is a transaction? What are its states? 2. Explain the ACID properties of a transaction. 3. What is a schedule? What is a serial schedule? 4. What is serializability? What are its types? 5. What is conflict serializability? 6. What is a precedence graph? How is it used? 7. What is a lock? What are the types of locks? 8. What is two-phase locking (2PL)? 9. What is strict 2PL? 10. What is a deadlock? How is it detected and resolved? 11. What is the timestamp ordering protocol? 12. What is a dirty read, non-repeatable read, and phantom read? 13. What is the write-ahead log (WAL) protocol? 14. What is a checkpoint? Why is it used? 15. What is shadow paging? --- ## Unit 5 — Storage & Indexing 1. What is file organization? Name its types. 2. What is indexing? What are its advantages? 3. What is the difference between dense and sparse index? 4. What is a primary index vs. a secondary index? 5. What is a clustered index vs. a non-clustered index? 6. What is a multi-level index? 7. What is a B-tree? What are its properties? 8. What is a B+ tree? How does it differ from a B-tree? 9. What is static hashing? 10. What is dynamic hashing (extendible hashing)? 11. What is query processing? What are its steps? 12. What is query optimization? 13. What is cost estimation in query optimization? --- ## Unit 6 — Advanced Topics 1. What is a distributed database? What are its advantages? 2. What is fragmentation? Name its types. 3. What is horizontal fragmentation vs. vertical fragmentation? 4. What is replication in a distributed database? 5. What is a NoSQL database? How does it differ from a relational database? 6. What are the types of NoSQL databases? 7. What is MongoDB? What is a document in MongoDB? 8. What is Big Data? What are its characteristics (5 Vs)? 9. What is a data warehouse? How is it different from a database? 10. What is data mining? 11. What is a cloud database? 12. What is database security? What are authorization and authentication?