SELECT sum(cumul_tonne),code_chapitre,bief_depart.b1,bief_depart.b2
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,bief_depart.b1