Código SQL [-] select sum(cast( case position('-',cve_art) when 0 then cve_art else substring(cve_art from 1 for position('-',cve_art)-1) end as double precision)) from nombreTabla
select sum(cast( case position('-',cve_art) when 0 then cve_art else substring(cve_art from 1 for position('-',cve_art)-1) end as double precision)) from nombreTabla