Very slow query, help please

[Jaume Roca]

Hello everyone.

I have a very slow query (33.1319 seconds) and I don't know if there is a solution for this:

select proveidors_treballadors.id_prov_treb, nom, coalesce(fac,0) from proveidors_treballadors
left join (select id_prov_treb, ROUND((sum(materials+stock)),2) as fac from albarans 
left join (select id_albara, sum(quantitat*multiplicatiu) as materials from comandes_albarans_families group by id_albara)
    T1 on (albarans.id_albara=T1.id_albara)
left join (select id_albara, sum(quantitat*multiplicatiu) as stock from albarans_families group by id_albara)
    T2 on (albarans.id_albara=T2.id_albara) 
group by id_prov_treb)
T3 on (proveidors_treballadors.id_prov_treb=T3.id_prov_treb)
where tipus_prov_treb = 'proveidor';

The query explain is



And design for data base, the tables are in yellow color:



Thank you!