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,'Same

Day')

FROM promos;

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

FROM promos;

Answer: D

解析：题目意思如果开始和结束为同一天，就输出’Same Day’

NULLIF(promo_start_date,promo_end_date) 如果两个表达式相同，则返回null