Generate table relationship diagram from existing schema (SQL Server)

Yes you can use SQL Server 2008 itself but you need to install SQL Server Management Studio Express (if not installed ) . Just right Click on Database Diagrams and create new diagram. Select the exisiting tables and if you have specified the references in your tables properly. You will be able to see the complete diagram of selected tables. For further reference see Getting started with SQL Server database diagrams

Try DBVis - download at https://www.dbvis.com/download - there is a pro version (not needed) and a open version that should suffice.

All you have to do is to get the right JDBC - database driver for SQL Server, the tool shows tables and references orthogonal, hierarchical, in a circle ;-) etc. just by pressing one single button. I use the free version for years now.