Hello, so I'm trying to learn relational database and I'm learning many2many right now. 

So I have an upper head and a lower head, and my conditional statement is "allowed users that are only lowerhead" but the problem is I can select the same user. 

Example.

Eunha = Upper Head
Anya = Lower Head

Now the problem is, Anya can select Anya herself because she is a lower head

This is my domain

[("x_studio_head", "=", "Lower Head")]

I'm trying to think is if user_id = to self, then don't include