试题与答案

在下列 SQL 语句中,______包含了不正确的定义语句。 I.CREATE T

题型:单项选择题

题目:

在下列 SQL 语句中,______包含了不正确的定义语句。 I.CREATE TABLE…CREATE VIEW…CREATE INDEX II.DROP TABLE…DROP VIEW…DROP INDEX III.ALTER TABLE…ALTER VIEW…ALTER INDEX

A.只有Ⅰ

B.只有Ⅱ

C.只有Ⅲ

D.Ⅰ和Ⅱ

答案:

参考答案:C

解析:关系数据库由模式、外模式和内模式组成,即关系数据库的基本对象是表、视图和索引。因此SQL 的数据定义功能包括定义表、定义视图和定义索引。由于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。

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