访问或 Mysql - 表行作为查询中的列

Question

I have these three tables:

The table "Clienti" contains the customers. The table "Corsi" contains all the available courses The table "corsi Fatti" contains all the Courses each client has taken.

what I would need is a query that returns each client, and what courses he attended on what date. For that I would like to have for example a table returned with these columns:

Clienti.Nome, corsi.row1.corso, corsi.row2.corso, corsi.row3.corso,corsi.rowN.corso.

and the content of the table should be: clienti.Nome, corsifatti.data of the matching course in the corsi table if present.

so, first column is the client name, and then there is a column for each row of the "corsi" table, and if a client has partecipated on that course then the corsifatti.data should be in that column.

Can something like this be done with a Access or Mysql Query? I have tried with inner joins but the result was not what I need.

select
  Clienti.nome, Clienti.Addresse, Clienti.CAP, Clienti.Tel,
  Clienti.Ansprechpartner, Clienti.Mail, Clienti.Weiteres,
  CorsiFatti.Data, Corsi.Corso, Corsi.Durata 
from Clienti 
INNER JOIN CorsiFatti on CorsiFatti.[ID Cliente] = Clienti.ID 
INNER JOIN Corsi on Corsi.ID = CorsiFatti.[ID Corso]

Answer 1

What you are asking is a simple inner join:

select Clienti.nome, Clienti.Addresse, Clienti.CAP, 
   Clienti.Tel, Clienti.Ansprechpartner, Clienti.Mail, 
   Clienti.Weiteres, 
   CorsiFatti.Data, 
   Corsi.Corso, Corsi.Durata 
from Clienti 
INNER JOIN CorsiFatti on CorsiFatti.[ID Cliente] = Clienti.ID 
INNER JOIN Corsi on Corsi.ID = CorsiFatti.[ID Corso]
order by Clienti.nome, Corsi.Corso;

I think you meant yours was lacking the order by only. I wouldn't suggest using access, but if it is access anyway, then you need to have parenthseses around all those joins (peculiar I know, but it is access).

Answer 2

The pivot with variable columns count is complicated. I can advice simplest solution uses JSON aggregation:

SELECT 
  ClienteId, 
  Name, 
  JSON_ARRAYAGG(
    JSON_OBJECT("Data", Data, "Corso", Corso)
  ) Corsi 
FROM 
  CorsiFatti 
  JOIN Corsi ON Corsi.Id = CorsiFatti.CorsoId 
  JOIN Clienti ON Clienti.Id = CorsiFatti.clienteId 
GROUP BY 
  ClienteId, 
  Name
;

Result is row for each client contains client's data at his courses as JSON string:

+===========+=========+========================================================================================+
| ClienteId | Name    | Corsi                                                                                  |
+===========+=========+========================================================================================+
| 1         | Mr. Fix | [{"Data": "2021-01-01", "Corso": "Corso1"}, {"Data": "2021-02-01", "Corso": "Corso3"}] |
+-----------+---------+----------------------------------------------------------------------------------------+

Here you can find SQL fiddle