Oracle: Modifying Data & Multiple Databases MCQs

UPDATE emp SET salary = SELECT MAX(salary) FROM emp WHERE id = 5;
UPDATE emp WITH (SELECT MAX(salary)) WHERE id = 5;
UPDATE emp SET salary = FROM (SELECT MAX(salary)) WHERE id = 5;
UPDATE emp SET salary = (SELECT MAX(salary) FROM emp) WHERE id = 5;

Inserts the first row only
Inserts into all tables whose condition is true
Inserts each row only into the first table whose condition is true
Inserts rows in sorted order

Disables all locks
Lets a block run its own independent transaction that commits separately
Turns off logging
Rolls back the main transaction

Readers block all writers
Writers always block readers
Readers do not block writers, and writers do not block readers
Oracle locks the whole table for each update

LOCK emp EXCLUSIVE;
SET LOCK emp EXCLUSIVE;
LOCK TABLE emp IN EXCLUSIVE MODE;
ALTER TABLE emp LOCK;

Waits forever
Skips the locked rows silently
Returns an error immediately instead of waiting
Deletes the locks

READ COMMITTED
SERIALIZABLE
READ UNCOMMITTED
REPEATABLE READ

SET TRANSACTION READ ONLY;
SET TRANSACTION SNAPSHOT;
ALTER SESSION FREEZE;
SET LOCK READ;

SERIALIZABLE
READ COMMITTED
AUTOCOMMIT
READ ONLY

A table is locked
The redo log is full
The undo data needed for read consistency has been overwritten
A password has expired