OCP-1Z0-051-2015-48题

QUESTION NO: 48

Which two statements are true regarding views? (Choose two.)

A. A sub query that defines a view cannot include the GROUP BY clause

B. A view is created with the sub query having the DISTINCT keyword can be updated

C. A Data Manipulation Language (DML) operation can be performed on a view that is created

with the sub query having all the NOT NULL columns of a table

D. A view that is created with the sub query having the pseudo column ROWNUM keyword cannot

be updated

Answer: C,D

Explanation:

Rules for Performing DML Operations（select、update、insert、delete） on a View

You cannot add data through a view if the view includes:

Group functions

A GROUP BY clause

The DISTINCT keyword

The pseudocolumn虚拟数据行 ROWNUM keyword

Columns defined by expressions
NOT NULL columns in the base tables that are not selected by the view

A错误，创建视图的子查询可以使用group by子句。
B错误，子查询中带有DISTINCT 不能对视图进行DML操作。
C正确，所有非空列都可以进行DML操作。
D正确，子查询中带有ROWNUM 关键字不能对视图进行DML操作。