Today I have got "sqlproj is not supported by this version" error while opening my solution in Visual Studio 2010. The reason was I have installed VS 2012, while migration the database project extension got changed from *.dbproj to *.sqlproj. Basically VS 2012 converts .dbproj files into .sqlproj files, which VS 2010 can’t open. To resolve the issue of *.sqlproj interoperability, install the SQL Server Data Tools (SSDT) for VS 2012 and VS 2010.
You can download the SSDT from http://msdn.microsoft.com/en-us/data/hh297027
You can download the SSDT from http://msdn.microsoft.com/en-us/data/hh297027