I have a SQL Database. I would create an ER diagram in Gliffy (site). Gliffy only imports files from Microsoft Visio. So I don't how to export my DB from SQL Server in Visio to create the diagram there and importing the same into Gliffy.
Any ideas? There are other tools I can use to do this?
Visio professional (except Visio 2013) has a "reverse engineer" feature. You can use it to create a diagram of your existing SQL Server database. See here for example:
Reverse engineering an existing database
Reverse and forward engineering databases in Visio 2010