Hi Nicola,
You can use SQL Server Express for Workgroup geodatabases, this is what Workgroup geodatabases (multiuser) are designed for an supported on. These are the same as Enterprise Geodatabases on SQL Server, Oracle, etc.... The differences are related to the limitations on the number of connections allowed (an Esri limit of 10 for Workgroup licensing and 3 for Desktop licensing) and then the limits that Microsoft puts on the SQL Server Express installation:
Microsoft limits the use of SQL Server Express to one CPU (or core within a socket) and 1GB of RAM. The maximum database size for SQL Server 2005 or 2008 Express is limited to 4GB. The maximum database size for SQL Server 2008 Express R2 is 10GB. (Consult your Esri license agreement for specific information on the instance size limitations for your implementation.) |
Types of geodatabases—ArcGIS Help | ArcGIS for Desktop
Using Workgroup authorization/licensing on SQL Server Standard/Enterpise is not supported for creation of Enterprise Geodatabases.
Here are some other similar post on GeoNet with more information:
Can you install ArcGIS for Server Advanced Enterprise on SQL Server Express
How to configure existing SQL Server Express database for use with ArcGIS for Server Enterprise
ArcSDE for SQL server express
Hope this help with the confusion.....
-George
--- George T.