Normalization, query processing and optimization, transaction processing, concurrency control and recovery techniques. - One Line Questions

1. Which of the following is an example of a multi-valued dependency? — A ->> B
2. What is a transitive dependency in the context of normalization? — A dependency where a non-key attribute is determined by another non-key attribute, which in turn is determined by the primary key.
3. What is a 'lock' in the context of concurrency control? — A mechanism that restricts access to data items by concurrent transactions.
4. What is a transaction in the context of database management systems? — A sequence of database operations performed as a single logical unit of work.
5. What is a deadlock in transaction processing? — A situation where two or more transactions are waiting indefinitely for each other to release resources.
6. In a two-phase locking (2PL) protocol, what happens during the 'growing phase'? — A transaction can acquire locks but not release them.
7. If a deadlock is detected, what is a common recovery strategy? — Abort all transactions involved in the deadlock.
8. Which of the following is a common transaction state? — Active
9. A transaction that has been successfully completed and its effects are permanently recorded is in which state? — Committed
10. The 'Atomicity' property of a transaction ensures that: — All operations within the transaction are completed successfully, or none of them are.
11. Which ACID property ensures that once a transaction is committed, its changes are permanent and will survive system failures? — Durability
12. A relation is in Boyce-Codd Normal Form (BCNF) if for every non-trivial functional dependency X -> Y, X is a superkey. What is the main difference between 3NF and BCNF? — BCNF requires that every determinant must be a candidate key.
13. Which of the following is a common recovery technique that uses a log of all database modifications? — Write-Ahead Logging (WAL)
14. Which of the following is a type of normalization? — Third Normal Form (3NF)
15. The 'Isolation' property of a transaction ensures that: — Each transaction executes as if it were the only transaction running.
16. Which of the following is a common technique used in query optimization? — Cost-based optimization using statistics about the data
17. Which normal form requires that all non-key attributes are fully functionally dependent on the primary key? — Second Normal Form (2NF)
18. In which normal form are all transitive dependencies removed? — Third Normal Form (3NF)
19. Fourth Normal Form (4NF) addresses which type of dependency? — Multi-valued dependencies
20. A schedule is considered 'serializable' if: — It produces the same final database state as some serial execution of the same transactions.
21. What is a potential problem with two-phase locking (2PL)? — It can lead to deadlocks.
22. Which concurrency control mechanism uses timestamps to order transactions and detect conflicts? — Timestamp-based protocols
23. In the context of Write-Ahead Logging (WAL), what does 'write-ahead' mean? — Log records must be written to stable storage before the corresponding data block is written.
24. Consider a relation R(A, B, C, D) with functional dependencies {A -> B, C -> D}. If R is decomposed into R1(A, B) and R2(C, D), what type of decomposition is this? — Lossless join decomposition
25. Consider a join operation. Which of the following is NOT a common join algorithm? — Indexed Join
26. What is the minimal requirement for a relation to be in First Normal Form (1NF)? — All attributes are atomic.
27. Which heuristic rule in query optimization aims to perform selections and projections as early as possible? — Minimizing intermediate results
28. Which of the following is a typical stage in query processing? — All of the above
29. Which isolation level prevents dirty reads, non-repeatable reads, and phantom reads? — Serializable
30. What is a 'dirty read' in the context of transaction isolation levels? — Reading data that has not yet been committed.
31. What is a 'phantom read' in transaction isolation? — A transaction re-executing a query and finding new rows that match the query's criteria due to another committed transaction's insertions.
32. Consider a transaction T that aborts. What action does the recovery manager take? — Undo T's operations.
33. What does the 'Consistency' property of a transaction guarantee? — That the transaction will bring the database from one valid state to another valid state.
34. What is a schedule in the context of transaction processing? — The order in which the operations of concurrent transactions are interleaved.
35. Which of the following is a characteristic of a lossless join decomposition? — The original relation can be reconstructed by performing a natural join of the decomposed relations.
36. What is a query plan or execution plan? — A structured representation of the steps the database system will take to execute a query.
37. What is a 'log record' in the context of recovery? — Information about a database operation (e.g., the data modified, the old and new values).
38. Which technique can be used to detect deadlocks? — Both timeouts and wait-for graphs
39. What is the purpose of a cost model in query optimization? — To estimate the computational cost (e.g., I/O, CPU) of different query execution plans.
40. What is the primary goal of concurrency control in a database system? — To prevent database corruption due to simultaneous access by multiple transactions.
41. What is the primary goal of normalization in a relational database? — To reduce data redundancy and improve data integrity
42. What is the role of a 'checkpoint' in recovery? — To periodically save the state of the database to stable storage, reducing the amount of redo needed during recovery.
43. What is the purpose of the 'undo' operation during recovery? — To reverse the effects of aborted or failed transactions.
44. In query processing, what is the primary goal of query optimization? — To find the most efficient execution plan for a query.
45. What is the purpose of the 'redo' operation during recovery? — To reapply the changes of committed transactions that may not have reached stable storage.
46. What is the purpose of recovery techniques in a database system? — To ensure data consistency and durability in the event of failures.
47. In query optimization, what is the role of database statistics? — To provide information about the data distribution (e.g., number of distinct values, min/max values) to estimate the cost of operations.
48. Consider a transaction T that committed successfully but the system crashed before its changes were written to disk. What action does the recovery manager take? — Redo T's operations.
49. Which recovery technique involves creating shadow copies of data pages? — Shadow Paging
50. If a relation is in 3NF, is it necessarily in 2NF? — Yes
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