第53题062题库2019年OCP认证062考试新题

Posted 2022-02-17 cnblogs5359

53题、choose two

The HR user executes the following query on the EMPLOYEES table but does not issue COMMIT, ROLLBACK, or any data definition language (DDL) command after that:

SQL> SELECT job 

FROM employees

WHERE job=‘CLERK‘ FOR UPDATE OF empno;

HR then opens a second session.

Which two operations wait when executed in HR‘S second session?

A) SELECT job FROM employees WHERE job=‘CLERK‘ FOR UPDATE OF empno;

B) INSERT INTO employees(empno,ename,job) VALUES (2001,‘Harry‘,‘CLERK‘);

C) SELECT empno,ename FROM employees WHERE job=‘CLERK‘;

D) INSERT INTO employees(empno,ename) VALUES (1289,‘Dick‘);

E) LOCK TABLE employees IN EXCLUSIVE MODE;

Answer：AE

(解析：因为查询中用到了for update of，那么被查询到的行会被加锁，所以A答案会造成等待，E答案因为要锁整个表，所以也要发生等待。来自3组：1015267481)