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
原文：http://www.cnblogs.com/perfei/p/6245728.html