Microsoft SQL Server Express

Microsoft Desktop Engine (MSDE)

• Limited to 2GB databases Size

SQL Server 2005 Express and SQL Server 2008 Express

• Limited to 4GB databases Size
• Limited to 1 CPU (multiple core) and 1 GB RAM

SQL Server 2008 R2 Express 

• http://www.microsoft.com/sqlserver/2008/en/us/R2Downloads.aspx
• Limited to 10GB databases Size
• Limited to 1 CPU (multiple core) and 1 GB RAM
• No SQL Server Agent service
• Features Supported by Various Editions – http://msdn.microsoft.com/en-us/library/cc645993(v=SQL.105).aspx

SQL Server 2012 Express

• http://www.microsoft.com/en-us/sqlserver/editions/2012-editions/express.aspx
• Limited to 10GB databases Size
• Limited to 1 CPU (4 core) and 1 GB RAM
• No SQL Server Agent service
• Features Supported by Various Editions – http://msdn.microsoft.com/en-us/library/cc645993(v=sql.110).aspx