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 ;