DBMS QUIZ-III

In a database, you have a "Sales" relation that contains information about sales transactions, including the sale date. You want to find the maximum sale date. Which relational algebra operation would you use?

• SELECT

• PROJECT

• AGGREGATE

• JOIN

All NOT NULL columns from the base table must be included in the view in order for the INSERT  query to function.

• TRUE

• FALSE

• All NULL columns from the base table must be included in the view in order for the INSERT query to function

• None of the above

A user initiates a transaction to retrieve the average salary of employees from a table named employees. Which SQL statement should be used to calculate the average salary within the transaction?

• SELECT AVG(salary) FROM employees;

• CALCULATE AVERAGE salary FROM employees;

• AVERAGE SELECT salary FROM employees;

• GET AVG(salary) FROM employees;

An e-commerce website processes a customer's order, which involves deducting the item quantity from the inventory. If any part of the transaction fails, the system needs to revert all changes made by the transaction. Which SQL statement is used to roll back a transaction?

• ROLLBACK

• COMMIT

• SAVEPOINT

• REVERT

In a banking database, a customer initiates a fund transfer between two accounts. The transaction should either be fully completed or fully rolled back in case of an error. Which SQL statement is used to commit a transaction?

• COMMIT

• END TRANSACTION

• FINALIZE

• COMMIT TRANSACTION

A database application maintains employee records. An administrator initiates a batch process to update the salary of all employees. If any part of the batch fails, the system needs to roll back all changes made so far. Which SQL statement is used to set a savepoint within a transaction?

• SET SAVEPOINT

• SAVEPOINT

• DECLARE SAVEPOINT

• TRANSACTION SAVEPOINT

Scenario: A database contains a table named products with columns product_id, product_name, and price. A user initiates a transaction to update the price of a specific product with product_id = 102 to $25. Which SQL statement should be used to perform this update within the transaction?

• MODIFY products SET price = 25 WHERE product_id = 102;

• ALTER products SET price = 25 WHERE product_id = 102;

• UPDATE products SET price = 25 WHERE product_id = 102;

• CHANGE products SET price = 25 WHERE product_id = 102;

A user is updating multiple records in a table, and the changes should be visible to other users only after the entire transaction is committed. Which isolation level should be set for this transaction?

• READ UNCOMMITTED

• READ COMMITTED

• REPEATABLE READ

• SERIALIZABLE

A user initiates a transaction to update the status of multiple orders in a table. If any part of the transaction fails, the system needs to roll back the entire transaction. Which SQL statement is used to roll back a transaction?

• ROLLBACK

• CANCEL

• REVERT

• UNDO

You have a "Products" relation that contains information about products, including their prices. You want to find the products with a price less than $50. What relational algebra operation would you use?

• SELECT

• PROJECT

• JOIN

• DIFFERENCE