在子查詢中使用表別名與where子句對齊

Question

我剛開始學習MySQL，並對錶別名感到困惑。當我試圖運行此查詢，它告訴我的查詢無效：

select customer_number 
from 
(select customer_number, count(*) as num 
from orders 
group by customer_number) as tmp 
where num = (select max(num) in tmp) 

我知道有一個簡單的方法來做到這一點，我只是搞不清楚爲什麼我的代碼不能正常工作，非常感謝很多！

Answer 1

你可以修改你的使用LIMIT此查詢：

SELECT customer_number 
FROM orders 
GROUP BY customer_number 
ORDER BY COUNT(*) DESC 
LIMIT 1