幽默 ons which 原因 解析 table fonts 教程 The

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：

參考：

C不正確的原因為有其它列不能為空

D出錯，sum(quantity_sold)需要加個別名

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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OCP-1Z0-051-V9 02-2題