OCA lz0_007题库

Q: 41 Which two statements complete a transaction? (Choose two.)
A. DELETE employees;
B. DESCRIBE employees;
C. ROLLBACK TO SAVEPOINT C;
D. GRANT SELECT ON employees TO SCOTT;
E. ALTER TABLE employees
    SET UNUSED COLUMN sal;
F. SELECT MAX(sal)
    FROM employees
    WHERE department_id = 20;

Answer: D, E

解：

When Does a Transaction Start and End?
A transaction begins when the first DML statement is encountered and ends when one of the
following occurs:
• A COMMIT or ROLLBACK statement is issued
• A DDL statement, such as CREATE, is issued
• A DCL statement is issued
• The user exits iSQL*Plus
• A machine fails or the system crashes
After one transaction ends, the next executable SQL statement automatically starts the next
transaction.
A DDL statement or a DCL statement is automatically committed and therefore implicitly ends a
transaction.

 

SELECT                      Data retrieval

 

INSERT

UPDATE

DELETE

MERGE                       Data manipulation language (DML)

 

CREATE

ALTER

DROP

RENAME

TRUNCAZTE               Data definition language (DDL)

 

COMMIT

ROLLBACK

SAVEPOINT                Transaction control

 

GRANT

REVOKE                     Data control language (DCL)