Database Management Systems – Multiple Choice Questions (MCQs)

1. 37. What is a join operation in SQL?

   • A. Combining rows from two or more tables based on a related column
   • B. Filtering rows from a single table
   • C. Sorting rows in a table
   • D. Updating values in a table

2. 38. Which type of join returns only the rows where there is a match in both tables?

   • A. LEFT JOIN
   • B. RIGHT JOIN
   • C. INNER JOIN
   • D. FULL OUTER JOIN

3. 39. Which type of join returns all rows from the left table and matching rows from the right table?

   • A. LEFT JOIN
   • B. RIGHT JOIN
   • C. INNER JOIN
   • D. FULL OUTER JOIN

4. 40. Which type of join returns all rows from the right table and matching rows from the left table?

   • A. LEFT JOIN
   • B. RIGHT JOIN
   • C. INNER JOIN
   • D. FULL OUTER JOIN

5. 41. Which type of join returns all rows when there is a match in either left or right table?

   • A. LEFT JOIN
   • B. RIGHT JOIN
   • C. INNER JOIN
   • D. FULL OUTER JOIN

6. 42. What is a database transaction?

   • A. A sequence of operations performed as a single logical unit of work
   • B. A single SQL statement
   • C. A database backup
   • D. A user login session

7. 43. What does Consistency mean in ACID?

   • A. All operations in a transaction must be completed successfully
   • B. Transactions must be isolated from each other
   • C. The database must transition from one valid state to another valid state
   • D. Changes made by a committed transaction are permanent

8. 44. What does Isolation mean in ACID?

   • A. All operations in a transaction must be completed successfully
   • B. Multiple transactions should execute independently without interfering with each other
   • C. The database must remain consistent
   • D. Changes are permanent

9. 45. What does Durability mean in ACID?

   • A. All operations must be successful
   • B. Transactions must be isolated
   • C. The database must be consistent
   • D. Changes made by a committed transaction must be permanent

10. 46. What is concurrency control?

    • A. Managing simultaneous access to the database by multiple users
    • B. Ensuring data integrity
    • C. Optimizing query performance
    • D. Securing the database

11. 47. What is a lock in concurrency control?

    • A. A mechanism to restrict access to a database object
    • B. A way to speed up queries
    • C. A method for backup
    • D. A type of constraint

12. 48. What is a shared lock (read lock)?

    • A. Allows multiple transactions to read the same data concurrently
    • B. Allows only one transaction to read the data
    • C. Prevents any transaction from accessing the data
    • D. Allows a transaction to modify the data