071考試不僅是OCP11g的考試科目，同時也是OCP 12c的考試科目，所以關心071考題的同學有很多，對此我們專門收集整理了近期071考試的原題，并對這些考題進行講解，希望幫助廣大考生順利通過071考試。
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071考題解析-第51題、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，子查詢中如果有出現某行值為 null，則忽略該行，其它的正常處理，原來 051 的考題。
類似的語句：
select ename from emp where empno in (select mgr from emp);
ENAME
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FORD
BLAKE
KING
JONES
CLARK
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