OCP笔记001

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.)

create table sales(
prod_id number not null,
cust_id number not null,
time_id date not null,
channel_id number not null,
promo_id number not null,
quantity_sold number(10,2) not null);

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

CD选项，所创建视图不包含所有字段，视图不包含字段时默认为空，而SALES表所有字段皆不可为空，因此CD选项所创建的视图无法完成插入操作。

SQL> insert into v2 values(1,2,sysdate);
insert into v2 values(1,2,sysdate)
*
ERROR at line 1:
ORA-01400: cannot insert NULL into ("SCOTT"."SALES"."CHANNEL_ID")

而V3视图就可以

SQL> insert into v3 values(1,2034,sysdate,1,1,1);

1 row created.

SQL> commit;

Commit complete.

SQL> select * from v3;

   PROD_ID    CUST_ID TIME_ID         CHANNEL_ID   PROMO_ID QUANTITY_SOLD
---------- ---------- ------------------ ---------- ---------- -------------
     1     2034 03-JAN-17           1         1           1

5. Which SQL statements would display the value 1890.55 as $1,890.55? (Choose three .)

A. SELECT TO_CHAR(1890.55,'$0G000D00')
FROM DUAL;
B. SELECT TO_CHAR(1890.55,'$9,999V99')
FROM DUAL;
C. SELECT TO_CHAR(1890.55,'$99,999D99')
FROM DUAL;
D. SELECT TO_CHAR(1890.55,'$99G999D00')
FROM DUAL;
E. SELECT TO_CHAR(1890.55,'$99G999D99')
FROM DUAL;
Answer: ADE

注意字母类比如D，与符号类，比如”,”，只能出现一个，不能同时出现，因此排除C选项。

SQL> select TO_CHAR(1890.55,'$99,999D99') from dual;
select TO_CHAR(1890.55,'$99,999D99') from dual
                       *
ERROR at line 1:
ORA-01481: invalid number format model