大數據就業實戰培訓 Oracle就業實戰培訓
071考試題庫之前是比較穩定的，但隨著Oracle的調整，071考試不斷的增加新的考題，增加了考試的難度，所以我們專門收集整理了這些考試，并對這些考題進行解析，希望可以對考生有幫助。
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071考試-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
