Serials Dropdown list

-- url of the page with the problem -- : associazioneformatori.it
-- Joomla version -- : 3.8.7
-- PHP version -- : 7.1.0

Hello,
I should create a dropdown list of the serials for each user in a form. I built the form with Fabrik Joomla Component, but I have a problem to filter the serials by user.
I tried by the follow code:
WHERE {thistable}.`serial_id`
IN (SELECT nu8cw_hikaserial_serial.serial_id FROM nu8cw_hikaserial_serial LEFT JOIN nu8cw_users ON (nu8cw_hikaserial_serial.serial_user_id = nu8cw_users.id))

But I see all serials that users bought in the list.
Thank you in advance,
Vito

Hello Jerome,
I explain the form sense:
Each member fill in a personal report with some info including a serial number.
I created the form with all fields with Fabrik, including a dropdown menù where member should see his serials.
The dropdown menù is connected with hikaserial_serial table, but it's not filtered by the user login. After login each member goes in his personal page and see his serials, it's fine, but when open the page to fill in the report, all the serials appear in the dropdown menù.
Also the best solution should be that the member use the serial just one time.
Thanks,
Vito

Ok I will check it.
Thank you.

Hi Jerome,
is it possible to view the user's serials in a dropdown list? At moment I can see these list in a table.
Thank you,
Vito