title: Database Relationship or friend table design for a social networking site
body: <p>Hello Im in the midst of creating a social networking site and I would like to know how I would go about creating the relationships between users.  Many sites say that I should create a relationship/friend table, but Im looking into the future and believe that this would be ineffective. This idea could be as popular as facebook and I want to be ready for that many users.  Facebook has 400 million users so a friends table would be at least 150 times that.  Doing a query for ones friends would be very slow I would think.  So would the solution be a seperate table for each user containing their friends ID's. or an associated CSV file containing the ID's.  Any help would be greatly appreciated to the design of my site. Thanks</p>