ocp 11g考試題庫詳解：1Z0-051-105題
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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
試題解析：
A。NULLIF里面額數據類型為date與 'Same Day'字符串類型不匹配，錯誤。
B。TRUNC將小數部分截斷，但類型不一致，錯誤。
C。TO_CHAR(TRUNC(promo_end_date-promo_end_date))，如果相等，TRUNC為0，to_char后，字符為0，即始終有值，NVL2返回第二個值，即NULL
