best way to store 1:1 user relationships in relational database

Question

What is the best way to store user relationships, e.g. friendships, that must be bidirectional (you\'re my friend, thus I\'m your friend) in a rel. database, e.g. MYSql?

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Answer 1

I would have a link table for friends, or whatever, with 2 columns both being PK's, and both being FK's to the User table.

Both columns would be the UID, and you would have two rows per friend relationship (A,B and B,A). As long as both columns are PK's, it should still be in normal format (although others are free to correct me on this)

Its a little more complex of a query, but nothing that can't be abstracted away by a stored procedure or some business logic, and its in Normal Format, which is usually nice to have.