It depends a little on the scenario
1. Standard or Custom Tables
2. Virtual Tables
3. Many to Many relationships versus N1: or 1:N
For 1:N / N:1
For Standard or Custom (standard but not system) with 1:N N:1 , dataverse creates a reference between them, not.. per se linked to a specific field, as it can be the ID field, aka the unique identifier, or it can be a secondary key, so its not just limited to the GUID which is why I said its not
.
However, when you created your tables, when you create a relationship, it will have to show "something" in the column, so it will show the Primary Column that you assign, so pick that carefully so the data showing makes sense.
This will cause the creating table to have a Column, that will display the Primary Column Data in it (from the other record).
For Many to Many
Dataverse creates another entire back end "mapping" table that you cannot access or add to. It does this because its a matrix now of references, not a single one. You have no control over this table and you don't see them in the UI as a single column like 1:N or N:1
YOU can create your own Many to Many relationship by created your own table and then adding in rows where you associate records from A to records to B and vice versa
The benefit to this is, you can also add other data points to each row, which you cannot do with the built in hidden many to many. Many of the older timers and I did this because we wanted to track information between the two table or in even a polymorphic relationship, versus just storing GUID1 and GUID2 (and event) GUID3/4/5/ etc
It might be something like
students to classes where classes have many students and students have many classes, but you also want to track IF a user attended or not and what date. Doing your own Many to Many allows that.
For Virtual tables
You can have 2 types
1:N / N:1 and Custom multi-table (polymorphic) relationships
Normally you would leverage the primary unique field in Dataverse (the GUID), and then have that as a foreign key in your Virtual Table.
NOTE: You will hear Relationship and Many to one, but then see N:1 or 1:N and there is no wording of Many to one in the visual you pick :-)
This is how they work in the back end.
If this answers your Question please Mark as such and maybe a like :-)
If you have any other questions after please let me know
