OCP 1Z0 051 V9 02 2题

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2. View the Exhibit to examine the description for the SALES table.

Which views can have all DML operations performed on it? (Choose all that apply.) 

A. CREATE VIEW v3

AS SELECT * FROM SALES   

WHERE cust_id = 2034   

WITH CHECK OPTION;

B. CREATE VIEW v1

AS SELECT * FROM SALES   

WHERE time_id <= SYSDATE - 2*365   

WITH CHECK OPTION;

C. CREATE VIEW v2

AS SELECT prod_id, cust_id, time_id FROM SALES   

WHERE time_id <= SYSDATE - 2*365   

WITH CHECK OPTION; 

D. CREATE VIEW v4

AS SELECT prod_id, cust_id, SUM(quantity_sold) FROM SALES   

WHERE time_id <= SYSDATE - 2*365   

GROUP BY prod_id, cust_id   

WITH CHECK OPTION;

Answer: AB

答案解析：

参考：

C不正确的原因为有其它列不能为空

D出错，sum(quantity_sold)需要加个别名

sh@TESTDB> create view v4

  2  as select prod_id,cust_id,sum(quantity_sold) from sales

  3  where time_id<=sysdate-2*365

  4  group by prod_id,cust_id

  5  with check option

  6  ;

as select prod_id,cust_id,sum(quantity_sold) from sales

                          *

ERROR at line 2:

ORA-00998: must name this expression with a column alias

 

sh@TESTDB> create view v4

  2  as select prod_id,cust_id,sum(quantity_sold) sumqty from sales

  3   where time_id<=sysdate-2*365

  4  group by prod_id,cust_id

  5  with check option

  6  ;

 

           

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