You can create a view in a database and map the entity to the view. LINQ to SQL generates the same SQL for views as it does for tables.
Note
The use of views in this scenario has limitations. This approach works most safely when the operations performed on Table are supported by the underlying view. Only you know which operations are intended. For example, most applications are read-only, and another sizeable number perform Create/Update/Delete operations only by using stored procedures against views.