题目链接：​​点击打开链接​​

题目大意：略。

解题思路：略。

AC 代码

-- 解决方案(1)
SELECT ROUND(COUNT(IF(order_date = customer_pref_delivery_date, true, null)) / COUNT(1) * 100, 2) immediate_percentage
FROM Delivery

-- 解决方案(2)
select round (
    sum(case when order_date = customer_pref_delivery_date then 1 else 0 end) /
    count(*) * 100,
    2
) as immediate_percentage
from Delivery

-- 解决方案(3)
select round (
    sum(order_date = customer_pref_delivery_date) /
    count(*) * 100,
    2
) as immediate_percentage
from Delivery