I have a trouble in understanding SBO tables relationship. I can't find the relationship in SQL Server Diagram. Can anyone tell me how to solve this issue?
I haven't seen it in diagram format, but there are a couple of sources that will help you find out about some of the linkages.
The first is the query wizard and query interface in the product itself. If you use this it lists meaningful names against tables, and will automatically generate the correct joins between related tables.
The second is a file called DB_Help.chm. It contains a lot of relevant information about the database tables. I think this is available for download on the service marketplace.