NexusDB

What I do is create a new dictionary with the new structure. Call NewDict.IsEqual(OldDict) and if not equal I perform a restructure on the table using the new dictionary and a field mapper (to make certain that the data is preserved). In short it comes down to this code (works for compatible fields)?:

  procedure RestructureTable(aDatabase : TnxDatabase;
    const aTableName : String; aNewDict : TnxDataDictionary);
  var
    OldDict : TnxDataDictionary;
    Mapper : TnxTableMapperDescriptor;
    TaskInfo : TnxAbstractTaskInfo;
    Completed : Boolean;
    TaskStatus : TnxTaskStatus;
  begin
    OldDict := TnxDataDictionary.Create;
    try
      if aDatabase.GetDataDictionaryEx(aTableName, '', OldDict) <> DBIERR_NONE then
        Exit;
 
      if OldDict.IsEqual(aNewDict) then
        Exit;
 
      Mapper := TnxTableMapperDescriptor.Create;
      try
        Mapper.MapAllTablesAndFieldsByName(OldDict, aNewDict);
        Check(aDatabase.RestructureTableEx(aTableName, '', aNewDict, Mapper, TaskInfo));
        if Assigned(TaskInfo) then
          try
            while True do begin
              TaskInfo.GetStatus(Completed, TaskStatus);
              Application.ProcessMessages;
              if Completed then
                break;
            end;
          finally
            TaskInfo.Free;
          end;
      finally
        Mapper.Free;
      end;
    finally
      OldDict.Free;
    end;
  end;