MYSQL - 获取用户和最新购买数据

Question

I am trying to do a MYSQL query where I get the most recent purchase for a user and then see if falls within certain criteria. Here is the query I put together:

select
    users_purch.purch_date as purchase_date,
    users_purch.total_amount as purchase_amount,
    users.* 
from
    users 
left join
    (
        select
            max(date) as purch_date,
            user_id,
            total_amount 
        from
            users_purchases 
        group by
            user_id
    ) as users_purch 
        on users_purch.user_id = users.id 
where
    users_purch.purch_date < '2016-11-01' 
    and users_purch.total_cost < 112.49 
order by
    users_purch.purch_date desc

It seems that the query works but fails in certain aspects. For example, if a user has more than one purchase entry it is getting the max date but the amount as total_cost that the query retrieves is not from the same row as the max date. How can I rewrite this query to give me the most recent purchase record in its entirety?

Thanks!

Answer 1

You have to join once more to user_purchases table in order to get the information about the date:

select
    users_purch.purch_date as purchase_date,
    users_purch.total_amount as purchase_amount,
    users.* 
from
    users 
left join
    (
        select
            max(date) as purch_date,
            user_id
        from
            users_purchases 
        group by
            user_id
    ) as users_purch 
        on users_purch.user_id = users.id 
left join
   (
       select
          user_id,
          date,
          total_amount
       from
          users_purchases
   ) as users_purch2 on users_purch.user_id = users_purch2.user_id and
        users_purch2.date = users_purch.purch_date
where
    users_purch.purch_date < '2016-11-01' 
    and users_purch.total_cost < 112.49 
order by
    users_purch.purch_date desc