选择题 1. View the Exhibits and examine the structures of the PRODUCTS, SALES, and CUSTOMERS tables. You issue the following query:

A、 It executes successfully.
B、 It produces an error because the NATURAL join can be used only with two tables.
C、 It produces an error because a column used in the NATURAL join cannot have a qualifier.
D、 It produces an error because all columns used in the NATURAL join should have a qualifier.

【正确答案】 C

【答案解析】 题目问的是对于SQL语句查询输出哪项是正确的，自然连接查询结果列不能有别名限定词，实验如下：