MYSQL - Get User and Most Recent Purchase Data - php

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

Answer 2

due the group by you have in this select
if you need the amount of the max(date) rewrite extecting the proper amount
select
users_purch.purch_date as purchase_date,
users_purch.total_amount as purchase_amount,
users.*
from
users
left join
(
select t1.purch_date, t1.user_id, t2.total_amount from (
select
max(date) as purch_date,
user_id
from users_purchases
group by user_id ) t1
inner join (
date,
user_id,
total_amount
from users_purchases
) t2 on t1.user_id= t2.user_id, t1.purch_date = t2.date
) 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

Answer 3

You can try this one, mate:
SELECT
up.date AS 'purchase_date',
up.total_amount AS 'purchase_amount',
u.*
FROM
users u
INNER JOIN users_purchases up ON up.user_id = u.user_id
INNER JOIN (
# get max date per user_id
SELECT user_id, max(date) AS 'purch_date'
FROM users_purchases
GROUP BY user_id
) max_up ON
max_up.user_id
# join that date to get the correct total_amount
AND max_up.`purch_date` = up.`date`
WHERE
up.`date` < '2016-11-01'
AND up.total_amount < 112.49
GROUP BY u.user_id
ORDER BY up.`date` DESC;
Note
Max Date per user_id
Value of total_amount per Max Date
Grouped per user_id
Ordered descending using users_purchases.date