Section 18
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?
True
False
(*)
When you logout of Oracle, your
data changes are automatically rolled back. True or False?
True
False
(*)
Which of the following best
describes the term "read consistency"?
It
ensures that all changes to a table are automatically committed
It
prevents users from querying tables on which they have not been granted SELECT
privilege
It
prevents other users from querying a table while updates are being executed on
it
It
prevents other users from seeing changes to a table until those changes have
been committed (*)
COMMIT saves all outstanding
data changes? True or False?
True
(*)
False
If a database crashes, all
uncommitted changes are automatically rolled back. True or False?
True
(*)
False
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?
24000
78000
30000
48000
(*)
You need not worry about
controlling your transactions. Oracle does it all for you. True or False?
True
False
(*)
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
(*)
An
object privilege
A
database link
An
update statement
A
sequence
If Oracle crashes, your changes
are automatically rolled back. True or False?
True
(*)
False
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. (*)
Both
the UPDATE and the INSERT will be rolled back.
The
INSERT is undone but the UPDATE is committed.
Nothing
happens.
Which SQL statement is used to remove all the changes made
by an uncommitted transaction?
ROLLBACK
TO SAVEPOINT;
UNDO;
REVOKE;
ROLLBACK;
(*)
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, B,
and C
A and B
(*)
C
None of
the above
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?
There
is nothing you can do.
COMMIT
Del_Done;
ROLLBACK
to SAVEPOINT Del_Done; (*)
ROLLBACK
UPDATE;
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;
ROLLBACK
TO SAVEPOINT upd1_done; (*)
ROLLBACK
TO SAVEPOINT upd2_done;
ROLLBACK
TO SAVE upd1_done;
There
is nothing you can do; either all changes must be rolled back, or none of them
can be rolled back.
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 (*)
22
JANE
will receive an error message because she is not allowed to query the table
while BOB is updating it.
2
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