php mysql 从数据库中的三个表中选择信息

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.