php mysql select information from three tables from the database - php

Question

the customer search is carried out by card number (see table A customer) and the code used by me is this:
$id = $_POST['card_number'];
SELECT e.*, sum(u.points) as points, sum(u.cost) as cost,
max(date_format(u.date_points, '%e/%c/%Y')) as data
FROM `customer` AS e
INNER JOIN `points` AS u ON e.id_customer = u.id_customer
where card_number='$id'
now I expose my tables and then I explain my problem
Table A Customer:
it contains the information of the members
id_customer
name
card_number
1
Luca
1234567890
2
Mark
9876543210
Table B Points:
it contains the points accumulated and the cost incurred
id_points
id_customer
points
cost
1
1
5
20
2
2
10
40
3
1
20
60
4
2
35
35
Result:
customer with id_customer 1 has a total of 25 points
customer with id_customer 2 has a total of 45 points
Table C deducted points:
it contains the points that will be deducted at the next purchase
id_deducted
id_customer
points
1
1
5
2
2
15
Result:
customer with id_customer 1 straight 5 points total remaining 20 points
customer with id_customer 2 climbs 15 points, total remaining 30 points
my question is this how can i make the sum of points from table B - the sum of points from table c? how can i add it in the select?

Answer 1

If you want a single request to get all info you need, you can make subrequests like this:
SELECT
c.*,
(
SELECT
SUM(p.points)
FROM
points p
WHERE
p.id_customer = c.id_customer
) AS points,
(
SELECT
SUM(d.points)
FROM
deducted_points d
WHERE
d.id_customer = c.id_customer
) AS deducted_points
FROM
customer c;
The result would be as follows
id_customer
name
card_number
points
deducted_points
1
Luca
1234567890
25
5
2
Mark
9876543210
45
15
But it would be very slow on large amounts of users and points changes I think. So I'd do select from users and then loop through them making individual requests to points and deducted_points tables.