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

原创于 2016-03-08 10:44:42 发布 · 1.2k 阅读

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本文介绍了一种使用SQL全外连接来生成包含所有国家名称及其对应客户和销售详情（如果存在）的报告的方法。通过具体例子展示了如何正确地运用左外连接和右外连接来达到目的。

128.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);
答案：C
解析：题目要求可以看到两个all分别是显示所有的country names和customers，因此排除A，B，D，