Need Help: How to add (if not exists) related records in POST Method

@DMehaffy : Thanks for the reply.

I think I understand your explanation, but I don’t know how to write it(not to mention efficiently).
If it’s going to take 10-20 lines of code will be in great help to have it also as reference how to do similar actions in the future( when starting implementing more relationships). I guess what I’m trying to do is quite common case, but as I’m still learning, I never did it and I was hoping for example(with code) to help me understand.

If it’s too much to ask for someone to write the code for my simple example, then if anyone has this or similar case already implemented in his Strapi project (customized default create controller), please share.

Thank you