SELECT sum( cumul_tonne ) , code_chapitre?bief_depart.b1
FROM `fanny_tonnage` , bief_depart
WHERE fanny_tonnage.num_quai_depart = bief_depart.num_quai_depart
AND fanny_tonnage.num_quai_arrive = bief_depart.num_quai_arrive
AND bief_depart.b1 =bief_depart.b2
GROUP BY code_chapitre