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