Database programmin section 18

1. Which SQL statement is used to remove all the changes made by an uncommitted transaction?
ROLLBACK (*)

2. If a database crashes, all uncommitted changes are automatically rolled back. True or False?
True (*)

3. COMMIT saves all outstanding data changes? True or False?
True (*)

4. You need not worry about controlling your transactions. Oracle does it all for you. True or False?
False (*)

5. User BOB's CUSTOMERS table contains 20 rows. BOB inserts two more rows into the table but does not COMMIT his changes. User JANE now executes:
SELECT COUNT(*) FROM bob.customers;
What result will JANE see?
20 (*)

6. A transaction makes several successive changes to a table. If required, you want to be able to rollback the later changes while keeping the earlier changes. What must you include in your code to do this?
A savepoint (*)

7. Steven King's row in the EMPLOYEES table has EMPLOYEE_ID = 100 and SALARY = 24000. A user issues the following statements in the order shown:
UPDATE employees
SET salary = salary * 2
WHERE employee_id = 100;
COMMIT;
UPDATE employees
SET salary = 30000
WHERE employee_id = 100;
The user's database session now ends abnormally. What is now King's salary in the table?
48000 (*)

8. Examine the following statements:
INSERT INTO emps SELECT * FROM employees; -- 107 rows inserted.
SAVEPOINT Ins_Done;
CREATE INDEX emp_lname_idx ON employees(last_name);
UPDATE emps SET last_name = 'Smith';
What happens if you issue a Rollback statement?

The update of last_name is undone, but the insert was committed by the CREATE INDEX statement. (*)

9. If UserB has privileges to see the data in a table, as soon as UserA has entered data into that table, UserB can see that data. True or False?
False (*)

10. If Oracle crashes, your changes are automatically rolled back. True or False?
True (*)

11. Which of the following best describes the term "read consistency"?
It prevents other users from seeing changes to a table until those changes have been committed (*)

12. When you logout of Oracle, your data changes are automatically rolled back. True or False?
False (*)

13. Table MYTAB contains only one column of datatype CHAR(1). A user executes the following statements in the order shown.
INSERT INTO mytab VALUES ('A');
INSERT INTO mytab VALUES ('B');
COMMIT;
INSERT INTO mytab VALUES ('C');
ROLLBACK;
Which rows does the table now contain?
A dan B (*)

14. Examine the following statements:
INSERT INTO emps SELECT * FROM employees; -- 107 rows inserted.
SAVEPOINT Ins_Done;
DELETE employees; -- 107 rows deleted
SAVEPOINT Del_Done;
UPDATE emps SET last_name = 'Smith';
How would you undo the last Update only?
ROLLBACK to SAVEPOINT Del_Done; (*)

15. Examine the following statements:
UPDATE employees SET salary = 15000;
SAVEPOINT upd1_done;
UPDATE employees SET salary = 22000;
SAVEPOINT upd2_done;
DELETE FROM employees;
You want to retain all the employees with a salary of 15000; What statement would you execute next?
ROLLBACK TO SAVEPOINT upd1_done; (*)