OCP-1Z0-051-V9.02-105题

105. Examine the structure of the PROMOS table:

name              Null        Type

PROMO_ID          NOT NULL    NUMBER(3)

PROMO_NAME                   VARCHAR2(30)

PROMO_START_DATE NOT NULL    DATE

PROMO_END_DATE    NOT NULL    DATE

You want to display the list of promo names with the message 'Same Day' for promos that started and

ended on the same day.

Which query gives the correct output?

A. SELECT promo_name, NVL(NULLIF(promo_start_date, promo_end_date), 'Same Day') FROM promos;

B. SELECT promo_name, NVL(TRUNC(promo_end_date - promo_start_date), 'Same Day') FROM promos;

C. SELECT promo_name, NVL2(TO_CHAR(TRUNC(promo_end_date-promo_start_date)), NULL,'SameDay') FROM promos;

D. SELECT promo_name, DECODE((NULLIF(promo_start_date, promo_end_date)), NULL,'Same day') FROM promos;

Answer: D

答案解析：

A。NULLIF里面额数据类型为date与 'Same Day'字符串类型不匹配，错误。

B。TRUNC将小数部分截断，但类型不一致，错误。

C。TO_CHAR(TRUNC(promo_end_date-promo_end_date))，如果相等，TRUNC为0，to_char后，字符为0，即始终有值，NVL2返回第二个值，即NULL

sh@TEST0924>  SELECT promo_name, NVL2(TO_CHAR(TRUNC(promo_end_date-promo_end_date)), NULL,'SameDay') FROM PROMOTIONS;

PROMO_NAME                     NVL2(TO

------------------------------ -------

NO PROMOTION #

newspaper promotion #16-108

post promotion #20-232

newspaper promotion #16-349

internet promotion #14-471

D。实验验证：正确的。

scott@TESTDB> SELECT  DECODE((NULLIF('11-mon-01','11-mon-01')),null,'same') from dual;

 

DECO

----

same

scott@TESTDB> SELECT  DECODE(null,null,'same') from dual;

 

DECO

----

same