Update with SQLServer DataSnap and Delphi

Dear, I have a problem when you want to update with SqlServer. I am developing a program with a DataSnap server and I have this problem when I want to update a field in the DBGrid.

I know that the error is in the key field of the sql query or rather, it is the key field that belongs to the database (field: code).

I do not know how to develop the sql query with delphi and that it does not generate that problem with my key code field.

State 01000, SQL Error Code 3621
State 23000, SQL Error Code 2627

Server-side code:

function TTServerMethods.updateItems(cod: String; desc: string; const pre:Integer): String;
begin
 try
       if not EjemploDatasnap.Connected then
          EjemploDatasnap.Connected := true;


       if SQLDataSetUpdateItems.Active then
          SQLDataSetUpdateItems.Active := False;

       SQLDataSetUpdateItems.ParamByName('codigops').AsString := cod;
       SQLDataSetUpdateItems.ParamByName('descripcion').AsString := desc;
       SQLDataSetUpdateItems.ParamByName('precio').AsInteger := pre;
       SQLDataSetUpdateItems.ExecSQL;
       SQLDataSetUpdateItems.Active := True;
       //SQLDataSetIProductos.Active:=False;



   except on
   E: Exception do
    Result := E.Message;
 end;
end;

SQLDataSet code:

object SQLDataSetUpdateItems: TSQLDataSet
    SchemaName = 'JDario'
    CommandText = 
      'UPDATE productos SET Descripcion = :descripcion, Precio = :preci' +
      'o   WHERE   codigo = :codigops'
    MaxBlobSize = -1
    Params = <
      item
        DataType = ftString
        Name = 'descripcion'
        ParamType = ptInput
      end
      item
        DataType = ftInteger
        Name = 'precio'
        ParamType = ptInput
      end
      item
        DataType = ftString
        Name = 'codigops'
        ParamType = ptInput
      end>
    SQLConnection = EjemploDataSnap
    Left = 40
    Top = 280
  end

Client side code:

procedure TForm5.aceptarEdicionClick(Sender: TObject);
var client : TTServerMethodsClient;
var ds:TDataset;
var codigo : STring;
var Descripcion : STring;
var Precio : Integer;
begin
client :=   TTServerMethodsClient.Create(SQLConProductosGrid.DBXConnection);

begin

  ds := DBGrid1.DataSource.DataSet;

     if not SQLConProductosGrid.Connected  then
            SQLConProductosGrid.Connected := True;


    DBGrid1.SetFocus;


    codigo := ds.FieldByName('codigo').AsString;
    Descripcion := ds.FieldByName('Descripcion').AsString;
    Precio := ds.FieldByName('Precio').AsInteger;

    Label3.Caption := client.updateItems(codigo,Descripcion,Precio);
    ds.UpdateRecord;
    ds.Next;

end;