I want to show the user id in gf_entry_notes table. Currently user_id is 0 for all notes. When any entry saved in our database it shows the user_id in created_by column and that entry have subscription which generated the entry notes then why user_id is 0 in the entry notes table?
The user_id is 0 in the gf_entry_notes table when the note is added by the system. If you add an entry note from the back end, the note will have your user_id stored.
Screenshot of the entry_notes table from my installation (two notes have my user ID):