SQL通常不提供下列哪一种操作
A．修改索引定义
B．修改视图定义
C．修改索引定义和修改视图定义
D．修改表定义
参考答案：C
解析： 视图是基于基本表的虚表，索引是依附于基本表的，因此，SQL通常不提供修改视图定义和修改索引定义的操作。用户如果想修改视图定义或索引定义，只能先将它们删除掉，然后再重建。不过有些关系数据库产品，如Oracle，允许直接修改视图定义。
| 阅读理解。 | ||||||||||||
Internet Forum (论坛) | ||||||||||||
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| 1. Who likes Andy Lau the best? | ||||||||||||
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| A. Andyfan B. 1000 reasons C. Movieman D. Lindalee | ||||||||||||
| 2. Why did Andfan cry? | ||||||||||||
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| A. She was sad at a concert. B. She was angry with Jacky Cheung. C. She had a broken heart. D. She thought Andy Lau was very good-looking. | ||||||||||||
| 3. What's Movieman's opinion? | ||||||||||||
[ ] | ||||||||||||
| A. Andy is a better singer. B. Jacky is a better singer. C. They both sing well. D. Jacky is a better actor. | ||||||||||||
| 4. Lindalee thinks Jacky's Cantonese songs sound the best because _____. | ||||||||||||
[ ] | ||||||||||||
| A. Jacky has no experience singing in Mandarin B. Cantonese is his first language C. His Mandarin pronunciation is bad. D. Jacky's Mandarin songs are boring | ||||||||||||
| 5. Which of the following is true? | ||||||||||||
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| A. Nobody likes Andy's Movies. B. 1000 reasons has the same opinion as Lindalee. C.1000 reasons thinks Andy's voice is more special than Jacky's D.Andyfan has never seen an Andy Lau's concert. |