I have a question about modeling a mutual relationship. It seems basic but
I can't decide, maybe it is 6 of one a half dozen of the other.
In my system any user might be friends with another user, that means they
have a reciprocal friend relationship.
It seems I have two choices for modeling it.
1. I have a table with two columns userOne and userTwo. If John is friends
with Jane there will be one row for both of them.
2. I have a table with two columns owner and friend. If John is friends
with Jane there will be two rows, one that is {John, Jane} and another
{Jane, John}.
The first option has the advantage of saving table size. But queries are
more complex because to get John's friends I have to JOIN friends f ON
f.userA = "John" OR f.userB = "John" (not the real query, these would be
id's but you get the idea).
In the second option the table rows would be 2x but the queries would be
simpler -- JOIN friends f ON f.owner = "John".
There could be >1M users. Each user would have <200 friends.
Thoughts? Do I just choose one or is there a clear winner? TIA!
