How to make SQL UNION if there is not full data in the tables?

Question

MySQL

I have never been a programmer, but fifteen years ago I once built a similar query ... I remember that I somehow applied UNIONfictitious fields like O AS FIELD... And I also remember that I spent three weeks (or maybe more) on it. And now the brains are completely rusted and I can’t even figure out where to start. And you need something like this:
There is a "TAR" TABLE:

id1 |  НАЗВАНИЕ_ТАРЫ
----+-------------------------
01  |  Ящик
02  |  Корзинка
03  |  Грузовик

There is a "LOAD" TABLE:

id2 |  НАЗВАНИЕ_ГРУЗА
----+------------------------
01  |  Огурцы
02  |  Молоко
03  |  Туалетная бумага

There is a "TABLE OF RELATIONSHIPS":

link1 |  link2    | КОЛИЧЕСТВО
------+-----------+--------------------
01    |  01       |  15 
01    |  02       |  2
02    |  01       |  4
02    |  03       |  2
03    |  01       |  100
03    |  02       |  60
03    |  03       |  500

And I want to get:

НАЗВАНИЕ_ТАРЫ  |  НАЗВАНИЕ_ГРУЗА    |  КОЛИЧЕСТВО
---------------+--------------------+----------------
Ящик           |  Огурцы            |  15
Ящик           |  Молоко            |  2
Ящик           |  Туалетная бумага  |  0
Корзинка       |  Огурцы            |  4
Корзинка       |  Молоко            |  0
Корзинка       |  Туалетная бумага  |  2
Грузовик       |  Огурцы            |  100
Грузовик       |  Молоко            |  60
Грузовик       |  Туалетная бумага  |  500

That is, you need to get 0for the field КОЛИЧЕСТВОin cases where the objects are not connected through ТАБЛИЦА СВЯЗЕЙ. How?

Answer 1

table_box - container
table_product - cargo
table_link - link

SELECT t1.name, t2.name, IFNULL(t3.qty, 0) as qty FROM table_box as t1 
INNER JOIN table_product as t2 
LEFT JOIN table_link as t3 ON (t3.link1 = t1.id1 AND t3.link2 = t2.id2);