Four part identifiers are supported.

[ [ [ [ server. ] [ database ] . ] [ namespace ] . ] table .] column

• Server is reserved for future use.
• Database is the name of a loaded dataset. See the CREATE DATABASE command for how to load multiple datasets.
• Namespace corresponds to the DataTable.Namespace. Using different namespaces allows the same table to appear in a Dataset multiple times.
• Table corresponds to a DataTable.TableName or alias
  Column corresponds to DataColumn.ColumnName in a DataTable or alias

Use square brackets ([table].[column]) when a name contains spaces or matches a reserved keyword. Note that period (.) is not supported in any of the parts of an identifier.

The following is an example of a query containing a 3 part name:

SELECT * FROM [AdventureWorks].[HumanResources].[Employee];