Select Field using SQL: how to set default to 1st record

Thank you for your help.
I'm sorry to ask you where I should copy the example code that you suggested.
From your previous message, I understand that there should be a parameter to add the JS code but I was not able to locate where the parameter is and where to copy the JS code you sent to me.

Hello

-- the CUSTOM JS parameter is in item form TAB of component properties
-- and you can customize in content type parameters too, to have different JS per content type


this particular JS will not cause problem even if you load in any view, (so you could add to some JS file loaded by backend or frontend Joomla template) but better add to the parameter

Thank you so much.
Much clearer now.
I could locate both parameters (component and type) as per your indications.