071考试是OCP认证的一个重要科目,不少考生都在这里受伤,对此我们专门收集整理了近期071考试的原题,并对071题库进行了讲解,希望帮助大家顺利通过071考试。
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071考试原题分享-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
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FORD
BLAKE
KING
JONES
CLARK
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