OCP-1Z0-051-V9.02-128题

128. View the Exhibits  and examine the structures of the  CUSTOMERS,  SALES,  and COUNTRIES

tables.

You need to generate a report that shows all country names,  with corresponding customers (if any) and 

sales details (if any), for all customers.

Which FROM clause gives the required result?

A. FROM sales JOIN customers USING (cust_id)

FULL OUTER JOIN countries USING (country_id);

B. FROM sales JOIN customers USING (cust_id)

RIGHT OUTER JOIN countries USING (country_id);

C. FROM customers LEFT OUTER JOIN sales USING (cust_id)

RIGHT OUTER JOIN countries USING (country_id);

D. FROM customers LEFT OUTER JOIN sales USING (cust_id)

LEFT OUTER JOIN countries USING (country_id);

Answer: C

答案解析：

参考： http://blog.csdn.net/rlhua/article/details/12877591

显示 所有客户的 所有country names，对应的customers（如果有）和sales details（如果有）

即是左外连接 customers  ，显示所有客户，右外连接 countries  ，显示所有   country names。