These are the database tables and relationships behind User Interest Groups (UIG)

User Interest Groups

Each User Interest Group is held in dbo.UserCollections

Sites assigned to a UIG

Each UIG can have many sites assigned to it.  This is a many-to-many relationship, since one UIG can contain many sites and the same site can belong to one or many UIGs.  This relationship is held in table dbo.UserSites

Users assigned to a UIG

Each user can only belong to one UIG (but an UIG can have many users) and so this one-to-many relationship is managed in the dbo.Users table by holding the Primary Key of the UIG as an attribute of the User called UserCollection