071考试既是ocp11g的考试科目，又是ocp12c的考试科目，所以关注的人很多，由于071考试题多变，我们专门收集了近期的071考试原题，并对071考试进行了讲解，分享给大家。
--------------------------------------------
071考试原题-第51题、choose the best answer:
Evaluate the following SQL statement:
SQL> SELECT cust_id, cust_last_name
FROM customers
WHERE cust_credit_limit IN
(select cust_credit_limit
FROM customers
WHERE cust_city ='Singapore');
Which statement is true regarding the above query if one of the values generated by the subquery is NULL?
A) It ignores the NULL value and generates output for the other values produced by the subquery.
B) It produces an error.
C) It generates output for NULL as well as the other values produced by the subquery.
D) It executes but returns no rows.
Answer：A
(解析，子查询中如果有出现某行值为 null，则忽略该行，其它的正常处理，原来 051 的考题。
类似的语句：
select ename from emp where empno in (select mgr from emp);
ENAME
----------
FORD
BLAKE
KING
JONES
CLARK
-----------------------------------------------
OCP解析公开课时间：【每周五晚8点】
OCP解析公开课地址：https://ke.qq.com/course/326223
OCP解析群资料分享：1015267481 验证：ocp
另外，除了OCP公开课，OCM题库直播也同步进行中，OCM最新题库大爆料-【每周四晚8点】，【微信群直播】，可以联系咨询老师进群参与
