Examples of "when is good idea implement many-to-many relationships"?

Question

I ask this because need to understand/explain better with examples.

clasical examples like: an Article can be published in multiple Publication objects, and a Publication has multiple Article objects. (source)

I see is usefull for web2.0 for sharing features.

Answer 1

Actors <-> Movies is fairly common.

Answer 2

You don't need two different tables either. I have many friends, and many people have me as a friend.

Answer 3

Items<->Orders is a fairly common one.

Answer 4

• Library <-> Book
• Song <-> Album
• Song <-> Artist
• Book <-> Author
• Program <-> Computer
• and so on.

The point here being that these aren't examples of when it's a good idea to implement many-to-many relationships. These are good examples of relationships that are many-to-many relationships.

I make that distinction because many-to-many typically isn't a modeling choice: it's just what the data is (in the context of your model).

Answer 5

SO Question <-> Tags

Answer 6

Property <-> Owner Shared Bank Account <-> Account Holder (which is not the same as Shared Account <- Primary Holder)

Many-to-Many relations can span through domains and be reflective and transitive. Class Subject <-> Student <-> Instructor