如果我使用单独的ASP.NET成员资格数据库，我应该如何处理与用户表的关系？

If i use a separated ASP.NET Membership database what is the correct way to define the relations between the user tables and application data tables?. Should i create copies of the user tables and sync? or is ok to just create the Guid columns and enforce validation in the application code?, Are there any issues with performance that i should be aware of when separating databases?If i use a separated ASP.NET Membership databas