The value of the TCustomDADataSet.BaseSQL property is used to complete the refresh SQL statement, if the manually assigned TCustomDAUpdateSQL.RefreshSQL property contains only WHERE clause.
SQLGeneratorCompatibility: boolean = False;
If the manually assigned TCustomDAUpdateSQL.RefreshSQL property contains only WHERE clause, SDAC uses the value of the TCustomDADataSet.BaseSQL property to complete the refresh SQL statement. In this situation all modifications applied to the SELECT query by functions TCustomDADataSet.AddWhere, TCustomDADataSet.DeleteWhere are not taken into account. This behavior was changed in SDAC 4.00.0.4. To restore the old behavior, set the BaseSQLOldBehavior variable to True.