Building a mysql query - mysql

Question

I have such a base structure (short version)
Table Product:
product_id, name, status
1, Product 1, 1
2, Product 2, 1
3, Product 3, 1
4, Product 4, 1
99, Product 99, 1
Table Box:
box_id, name
1, Box 1
Table Product_To_Box:
box_id, product_id
1, 1
1, 2
1, 3
1, 4
1, 99
Table Url: (id = product_id from the table 'product')
url_id, id, url, language_id
1, 1, wp.pl, 1
2, 1, wp.pl, 2
3, 2, google.pl, 1
Table Language:
language_id, name
1, English
2, Polish
There is no problem when I need to download all the products from the table 'product', which is not present in table 'url' and are assigned a 'box_id'.
I do this query
SELECT p.product_id AS id FROM product p LEFT JOIN product_to_box p2b ON (p.product_id = p2b.product_id) WHERE NOT EXISTS (SELECT u.id FROM url u WHERE p.product_id = u.id) AND p2b.box_id = '1'
Return 3 products:
Product 3
Product 4
Product 99
However, he needs a query that will return the items as above but additionally also the products that have no connection to each language from the table 'language'
Query should return 4 products:
Product 2 - return the product because the table 'url' no entry for language_id = 2
Product 3
Product 4
Product 99
How would add another language to the table 'language', eg. Vietnam (language_id = 3) and Table 'url' would look like this
1, 1, wp.pl, 1
2, 1, wp.pl, 2
3, 2, google.pl, 1
3, 2, google.pl, 2
3, 3, google.com, 1
3, 3, google.com, 2
3, 4, onet.pl, 1
3, 4, onet.pl, 2
3, 99, interia.pl, 1
3, 99, interia.pl, 2
This query should return all products because the table 'url' there is no reference to language_id = 3
Product 1
Product 2
Product 3
Product 4
Product 99

Answer 1

So I think the problem with you query is the sub query "NOT EXISTS (SELECT u.id FROM url u WHERE p.product_id = u.id)". Currently your SQL query doesn't even look at the language table, so it doesn't matter if there is matching language_ids. However, if you want join all the tables together and show all product_to_box.id = 1 then the following query would work:
SELECT p.product_id AS id, url_id, url, l.name FROM product p LEFT JOIN product_to_box p2b ON (p.product_id = p2b.product_id)
LEFT JOIN url ON (p.product_id = url.id) LEFT JOIN language l ON (url.language_id = l.language_id)
WHERE p2b.box_id = '1';
This outputs the following:
+------+--------+-----------+---------+
| id | url_id | url | name |
+------+--------+-----------+---------+
| 1 | 1 | wp.pl | English |
| 1 | 2 | wp.pl | Polish |
| 2 | 3 | google.pl | English |
| 3 | NULL | NULL | NULL |
| 4 | NULL | NULL | NULL |
| 99 | NULL | NULL | NULL |
+------+--------+-----------+---------+
6 rows in set (0.00 sec)
The below SQL will show all product_id from the table 'product', that is not found in the table 'url' and do not have assigned all language_id from table 'language'. It checks to see if url.id or language_id is null.
SELECT p.product_id AS id, url_id, url, l.name FROM product p LEFT JOIN product_to_box p2b ON (p.product_id = p2b.product_id)
LEFT JOIN url ON (p.product_id = url.id) LEFT JOIN language l ON (url.language_id = l.language_id)
WHERE url.id is null or l.language_id is null;
+------+--------+------+------+
| id | url_id | url | name |
+------+--------+------+------+
| 3 | NULL | NULL | NULL |
| 4 | NULL | NULL | NULL |
| 99 | NULL | NULL | NULL |
+------+--------+------+------+
3 rows in set (0.00 sec)