計(jì)算順序不是先where后select嗎？為什么能用select計(jì)算出別名？
select distinct item_id,userbehavior.item_category,amount
from userbehavior
inner join (select item_category,max(amount) as 最高工資 from userbehavior group by item_category) as t
on userbehavior.item_category=t.item_category
where amount=最高工資;