OCP认证051考试题库：11g-v9.02-第146题

OCP认证051考试题库：11g-v9.02-第146题，完整题库请点击这里联系老师咨询了解

146. 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 produces an error.

B. It executes but returns no rows.

C. It generates output for NULL as well as the other values produced by the subquery.

D. It ignores the NULL value and generates output for the other values produced by the subquery.

Answer: C

试题解析：

这道题的意思是说：如果子查询出现的值是null会怎样?

1、首先运行子查询里面的sql语句，结果为null

2、如果子查询为null，那么结果也为null。