OCP-1Z0-051-V9.02-40题

40. View the Exhibit to examine the description for the SALES and PRODUCTS tables.

You want to create a SALE_PROD view  by executing the following SQL statement:

CREATE VIEW sale_prod

AS SELECT p.prod_id, cust_id, SUM(quantity_sold) "Quantity" , SUM(prod_list_price) "Price"    

FROM products p, sales s   

WHERE p.prod_id=s.prod_id

GROUP BY p.prod_id, cust_id;

   

Which statement is true regarding the execution of the  above statement? 

A. The view will be created and you can perform DML operations on the view. 

B. The view will be created but no DML operations will be allowed on the view. 

C. The view will not be created because the join statements are not allowed for creating a  view. 

D. The view will not be created because the  GROUP BY clause is not allowed for creating a  view. 

Answer: B

答案解析：

参考： http://blog.csdn.net/rlhua/article/details/12790467

A错误，此视图为复杂视图，带有group by子句，不能对视图进行DML操作，

B正确，可以创建成功，但不能进行DML操作。

sh@TESTDB> CREATE VIEW sale_prod

  2  AS SELECT p.prod_id, cust_id, SUM(quantity_sold) "Quantity" , SUM(prod_list_price) "Price"    

  3  FROM products p, sales s   

  4  WHERE p.prod_id=s.prod_id

  5  GROUP BY p.prod_id, cust_id;

 

View created.

C错误，可以通过join来连接两张表创建视图。

D错误，可以通过group by 子句来创建视图。