Relating wp_user, wp_usermeta, and a custom database table
I am working on a site for a non-profit that has collected data on their ‘Members’ (over 2,000 members). Members report their surgeries and experiences in order for the non-profit to collect data on risk, outcomes, etc. Each one is has already been assigned a unique Member Number however, I believe these numbers were generated manually by the guy who handled this in the past.
I want to create user accounts for all of these Members so they can log in and see their form submissions, edit contact info, interact with each other, etc. We are using Ultimate Member and have 4 custom roles depending on the type of Member they are.
My question is how can I make each of them a user and relate the current custom_datatable with their new wp_user account and profile (so if they send another report it would be updated in the custom_datatable and still be linked with their wp_user profile)?
What would be the correct way to relate/join custom_datatable, wp_user, and wp_usermeta?
I am not very experienced with this type of stuff but it’s been dropped into my lap and need help getting this right.