MySQL上的三表交汇

Question

Item_List Table:

Kaloys Table:

Nanays Table:

Hi, I have three tables as can be seen on the provided images and I'm lost on what to with this task which is to display the Combined List of products that Both Customers (kaloys an Nanays) need, including quantities. Well, I somehow displayed what both customer needs by entering

select Item_List.PID, Item_List.Product, Item_List.supID 
from Item_List where PID in (
   select PID from Kaloys union distinct select PID from Nanays
);

Initial Output:

but I don't know how to also display the Quantity Column as well. What should I do?

Answer 1

You need a FULL OUTER JOIN to do this. Since MariaDB does not implement those, you'll need to simulate them by combining a LEFT JOIN with a RIGHT JOIN . See below:

select
  l.*, x.kqty, x.nqty
from (
  select k.pid, k.qty as kqty, n.qty as nqty
  from kaloys k left join nanays n on k.pid = n.pid
  union
  select n.pid, k.qty, n.qty
  from kaloys k right join nanays n on k.pid = n.pid
) x
join item_list l on l.pid = x.pid