Question:
How do you make TClientDataSet sort on lookup or calculated
fields?
Answer:
In the fields editor, when creating a new field to be sorted
on, choose New Field from the context menu and choose
InternalCalc as the field type. Or if creating TFields in
code, make the TField.FieldKind fkInternalCalc instead of
fkCalc. fkInternalCalc is only available in ClientDataSets.