How to combine 2 MySQL-functions

Question

I have two SQL functions that I want to integrate in able to make a prestashop export with a single SQL query:

Function 1 joins data from different tables.
Function 2 converts multiple rows into a single row.

I am unable to have these functions work together... Let me describe the two functions.

FUNCTION 1

SELECT a.id_product, a.ean13, a.weight, b.id_product, b.name, c.id_product, c.id_tab, c.content
FROM ps_product AS a
INNER JOIN ps_product_lang AS b ON b.id_product = a.id_product
INNER JOIN ps_extraproducttab_product_lang AS c ON c.id_product = a.id_product

These INNER JOINS work fine:

+------------+---------------+-------------+-----------+--------+-------------------+
| id_product | ean13         |   weight    |   name    | id_tab |      content      |
+------------+---------------+-------------+-----------+--------+-------------------+
|         11 | 0000000000001 | 1000.000000 | product_A |      1 | some ingredients  |
|         11 | 0000000000001 | 1000.000000 | product_A |      2 | some allergenes   |
|         12 | 0000000000002 | 1500.000000 | product_B |      1 | other ingredients |
|         12 | 0000000000002 | 1500.000000 | product_B |      2 | other allergenes  |
+------------+---------------+-------------+-----------+--------+-------------------+

But I want to convert c somehow. The second INNER JOIN uses a table that has multiple rows on a single key (id_product):

+--------+------------+---------+-------------------+
| id_Tab | id_product | id_lang |      content      |
+--------+------------+---------+-------------------+
|      1 |         11 |       1 | some ingredients  |
|      2 |         11 |       1 | some allergenes   |
|      1 |         12 |       1 | other ingredients |
|      2 |         12 |       1 | other allergenes  |
+--------+------------+---------+-------------------+

I want to combine these rows first. Running this second function on table 'ps_extraproducttab_product_lang' does exactly that:

FUNCTION 2

SELECT t1.id_product, t1.content AS 'ingred', t2.content AS 'allerg'
FROM ps_extraproducttab_product_lang t1, ps_extraproducttab_product_lang t2
WHERE t1.id_product = t2.id_product
  AND t1.id_Tab = '1'
  AND t2.id_Tab = '2' 

It outputs:

+------------+-------------------+------------------+
| id_product | ingred            | allerg           |
+------------+-------------------+------------------+
|         11 | some ingredients  | some allergenes  |
|         12 | other ingredients | other allergenes |
+------------+-------------------+------------------+

I used this source, privided by Akina: https://dba.stackexchange.com/questions/236692/combining-multiple-rows-into-a-single-row-with-multiple-columns ( I still need to find out how to extend this code to a 3th and 4th id_Tab, although that is not the topic of my current question )

I am unable to integrate the above in a single query that would result into:

+------------+---------------+-------------+-----------+-------------------+-------------------+
| id_product | ean13         | weight      | name      | ingred            | allerg            |                  |
+------------+---------------+-------------+-----------+-------------------+-------------------+
|         11 | 0000000000001 | 1000.000000 | product_A | some ingredients  | some allergenes   |
|         12 | 0000000000002 | 1500.000000 | product_B | other ingredients | other allergenes  |
+------------+---------------+-------------+-----------+-------------------+-------------------+

How would you build a single SQL-query to get the above result?

Any help is appreciated!

Answer 1

Consider multiple CTEs if using latest versions of MySQL/MariaDB to your Prestashop platform. Be sure to use explicit joins (not implicit as DBA SE link uses) and avoid a, b, c table aliasing. Extend the self-joins to ps_extraproducttab_product_lang for the 3rd and 4th categories.

WITH ew AS
  (SELECT p.id_product, p.ean13, p.weight, pl.name
   FROM ps_product AS p
   INNER JOIN ps_product_lang AS pl
      ON p.id_product = pl.id_product
  ), ia AS 
  (SELECT t1.id_product, t1.content AS 'ingred', t2.content AS 'allerg' 
        , t3.content AS 'thirdcat', t4.content AS 'fourthcat'
   FROM ps_extraproducttab_product_lang t1
   INNER JOIN  ps_extraproducttab_product_lang t2
      ON t1.id_product = t2.id_product 
     AND t1.id_Tab = '1' AND t2.id_Tab = '2' 
   INNER JOIN  ps_extraproducttab_product_lang t3
      ON t1.id_product = t3.id_product AND t3.id_Tab = '3'
   INNER JOIN  ps_extraproducttab_product_lang t4
      ON t1.id_product = t4.id_product AND t4.id_Tab = '4'
  )

SELECT ew.id_product, ew.ean13, ew.weight, ew.name
     , ia.ingred, ia.allerg, ia.thirdcat, ia.fourthcat
FROM ew
INNER JOIN ia
   ON ew.id_product = ia.id_product

For earlier versions of MySQL (pre v8.0) or MariaDB (pre v10.2), use subqueries:

SELECT ew.id_product, ew.ean13, ew.weight, ew.name
     , ia.ingred, ia.allerg, ia.thirdcat, ia.fourthcat
FROM 
  (SELECT p.id_product, p.ean13, p.weight, pl.name
   FROM ps_product AS p
   INNER JOIN ps_product_lang AS pl
      ON p.id_product = pl.id_product
  ) ew
INNER JOIN 
  (SELECT t1.id_product, t1.content AS 'ingred', t2.content AS 'allerg'
        , t3.content AS 'thirdcat', t4.content AS 'fourthcat'
   FROM ps_extraproducttab_product_lang t1
   INNER JOIN  ps_extraproducttab_product_lang t2
      ON t1.id_product = t2.id_product 
     AND t1.id_Tab = '1' AND t2.id_Tab = '2' 
   INNER JOIN  ps_extraproducttab_product_lang t3
      ON t1.id_product = t3.id_product AND t3.id_Tab = '3'
   INNER JOIN  ps_extraproducttab_product_lang t4
      ON t1.id_product = t4.id_product AND t4.id_Tab = '4'     
  ) ia
   ON ew.id_product = ia.id_product