I am creating an ERM but I am slightly confused with design for the relationships. Say for example I have 2 tables, one table called Manager and one table called Branch. Obviously a manager belongs to a branch, and let's say the tables look something like this...
There can be 1 manager per branch therefore producing a one-to-one relationship. But which is the source/destination for the relationship?
Personally I would say manager is the source in this scenario but I may have this the wrong way around.
If the relationship is bijective, "source" and "target" is subjective. However, you have to pick a concrete way of representing the relationship. You can put the reference in either table, or have a separate link table - regardless of where you put it, both ID fields will be uniquely constrained. Unless there's other information to inform the choice, the decision is arbitrary.