I've asked this Question on https://stackoverflow.com/q/49202343/9113120 Before and got and Answer, But I would like to understand how to deal with this kind of relation:

In this Query: http://sqlfiddle.com/#!9/fee4c6/3/0

    SELECT d.`id`, COUNT(da.`doc_id`), COUNT(db.`doc_id`)
    FROM `docs` d
    
    LEFT JOIN `docs_scod_a` da ON da.`doc_id` = d.`id`
    LEFT JOIN `scod_a` a ON a.id = da.`doc_id`
    
    LEFT JOIN `docs_scod_b` db ON db.`doc_id` = d.`id`
    LEFT JOIN `scod_b` b ON b.`id` = db.`doc_id`
    
    GROUP BY d.`id`;

`scod_a: a.id` depends on `docs_scod_a: da.doc_id` which depends on `docs: d.id`

What I want to do is `SELECT` the `id`s from `Table: docs` with the `COUNT()` of their related `doc_id`s from `Table: docs_scod_a, docs_scod_b`, Which is supposed to give me:

    | id | COUNT(da.`doc_id`) | COUNT(db.`doc_id`) |
    |----|--------------------|--------------------|
    |  1 |                  3 |                  3 |
    |  2 |                  3 |                  1 |
    |  3 |                  2 |                  3 |
    |  4 |                  0 |                  1 |

Then I filter the values using the `IN() clause` with `Table: scod_a, scod_b` columns of `ver_a, ver_b` by order using 

`WHERE a.ver_a IN ('AA') AND b.ver_b IN ('BA')`: http://sqlfiddle.com/#!9/fee4c6/21/0

What I expect the results having the `AA` and `BA` to return only the `ROW`s having `AA` from `Table: scod_a` and `BA` from `Table: scod_b` so the result would be:

    | id | COUNT(da.`doc_id`) | COUNT(db.`doc_id`) |
    |----|--------------------|--------------------|
    |  1 |                  3 |                  3 |

But as I mentioned in the previous Question, I get without `IN clause` the values:

    | id | COUNT(da.`doc_id`) | COUNT(db.`doc_id`) |
    |----|--------------------|--------------------|
    |  1 |                  9 |                  9 |
    |  2 |                  3 |                  3 |
    |  3 |                  6 |                  6 |
    |  4 |                  0 |                  1 |

And with `IN clause` the values:

    | id | COUNT(da.`doc_id`) | COUNT(db.`doc_id`) |
    |----|--------------------|--------------------|
    |  1 |                  9 |                  9 |


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 I want to understand What is the proper way to deal with these types of Queries with the shown example, Not just to solve the Problem.


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It is more about how do I use `IN() clause` within 3-Tables Relation, But with 6-Tables, 3 for Each type 

like here for `scod_a` and `docs_scod_a` only

http://sqlfiddle.com/#!9/f9a33f/5/0

But I want to add the `scod_b` and `docs_scod_b` too into the query as in the main query 

http://sqlfiddle.com/#!9/fee4c6/21/0 

Which didn't work and gave false values