Rest e Json

Olá pessoal, muito boa a edição 119 da revista Clube Delphi:   Estou com um problema(Coluna do Rodrigo Carreiro Mourão):   No trecho de código:   function TCliente.GetCustomersJson(OrderBy: string): TJSONArray;
var
  Sql: TStringBuilder;
  Reader: TDBXReader;
  Obj: TJSONObject;
  I: Integer;
begin
  Result := TJSONArray.Create;
  Sql := TStringBuilder.Create;
  Sql.Append('Select Cust_no, Customer, Address_Line1, ');
  Sql.Append('       City, Country, Phone_no From Customer ');
  if OrderBy <> EmptyStr then Sql.Append(' Order by '+OrderBy);

  DataSet.Text := Sql.ToString;
  Reader := DataSet.ExecuteQuery;

  Obj := TJSONObject.Create;
  for I := 0 to Reader.ColumnCount - 1 do
  begin
    Obj.AddPair(Reader.ValueType[I].Name,TJSONString.Create(Reader.ValueType[I].Name));
  end;
  Result.AddElement(Obj);

  while Reader.Next do
  begin
    Obj := TJSONObject.Create;
    Obj.AddPair('Codigo', TJSONNumber.Create(Reader.Value[0].GetInt32));
    Obj.AddPair('Nome', TJSONString.Create(Reader.Value[1].GetAnsiString));
    Obj.AddPair('Endereco', TJSONString.Create(Reader.Value[2].GetAnsiString));
    Obj.AddPair('Cidade', TJSONString.Create(Reader.Value[3].GetAnsiString));
    Obj.AddPair('Pais', TJSONString.Create(Reader.Value[4].GetAnsiString));
    Obj.AddPair('Telefone', TJSONString.Create(Reader.Value[5].GetAnsiString));
    Result.AddElement(Obj);
  end;
end;
Como eu consigo inserir campos do tipo: -Double (exemplo salary do EMPLOYEE.FDB) -Data   Obrigado: