OCP-1Z0-051-题目解析-第41题

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41. Which two statements are true regarding views? (Choose two.)
A. A subquery that defines a view cannot include the GROUP BY clause.
B. A view that is created with the subquery having the DISTINCT keyword can be updated.
C. A view that is created with the subquery having the pseudo column ROWNUM keyword cannot be updated.
D. A data manipulation language ( DML) operation can be performed on a view that is created with the subquery having all the NOT NULL columns of a table.

Answer: CD

A：子查询定义视图不能使用group by 子句（错误，有group by 子句的视图是复杂视图）
B：带有Distinct关键字的视图能被更新（错误，Distinct是去重复后的数据）
C：子查询中包含伪列rownum的视图不能被更新（正确）
D：通过子查询建立的视图，含有基表所有的非空列，可以执行DML操作（正确）

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