Architecture to avoid loops

[#1]

Hello,

I am facing the following problem (see attached diagram).

I have 2 systems (SysA and SysB) with some databases (SQL and MySQL).

Both have tables related to users and projects.

Both contain different information (ie one table has the user name while the other has its telefon number) and I would like to aggregate that.

I already 'joined' the projects tables using the AS keyword to rename the key in both project tales.

Now I would like to do the same with the users but it creates loops.

What is the best approch to handle this?

[hallquist_nate]

Whenever I have an association challenge like this, I turn to the Link Table model.  It has yet to fail me in the most complex association situations.

[#3]

Can you point me to the documentation on the Link table model?