Microsoft SQL Server 2008 Express Edition is a great database engine that is more than capable of handling most small business database requirements. There are however some limitations. The details below outline the main limitations in SQL 2008 Express Edition.
(Note: This information is not for SQL Server 2008 R2. If you are after the details for the limitations on SQL Server 2008 R2, please check out Microsoft SQL Server 2008 R2 Express Limitations).
1 CPU (based on a socket). No limit on cores.
Maximum of 1GB for the database engine.
(Note: SQL 2008 Express Edition with Advanced Services includes reporting features, and has a limit of 4GB for the reporting services. It still has a 1GB limit for the database engine).
The maximum database size is 4GB.
(Note: SQL Server 2008 R2 has increased this limit from 4GB to 10GB. If you need more than 4GB, please upgrade to SQL Server 2008 R2).
For a full rundown of the features that each SQL 2008 editions have included, you can visit http://msdn.microsoft.com/en-us/library/cc645993(v=sql.100).aspx