sqlite android select sum

my table look like this:

Client_Code    Oder_ID  NoOrd   Weight
850458         5        1       12
850458         5        2       12
850458         6        1        5   

i want to sum the Weight, but unique par Oder_ID. so the resultat that i want is 17 = 12 + 5 not 29

how can i do that ?

my code like this;

public int GetPoids()
    {           
        String SQL_syntax = "SELECT SUM("+ DBHelper.KEY_Poids +") as SumPoids FROM " +  DBHelper.tableName + " GROUP BY " + DBHelper.KEY_CodeClient +","+DBHelper.KEY_NoOrdre ;
        Cursor c = database.rawQuery(SQL_syntax, null);

         if (c != null)
                c.moveToFirst();

        int Poids = c.getInt(0);
        c.close();       

        return Poids;        
    }