Am reusit pana la urma sa reduc la 3 sec
with tmp(pk_key, cod)
As
(
    select max(pk_key) as pk_key cod from tabel where data <= @data group by cod
)
select pk_key, cod, sold, substring(cod,3,4) as grupa
from tabel t1 join tmp on t1.pk_key = tmp.pk_key
where t1.sold <> 0 and substring(t1.cod,1,2) = @comp
order by cod

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Sorin Sandu