Superquery's

select materia, count(*)/(select count(*) from financieras) as probabilidad from financieras where materia in(select distinct materia from financieras) group by materia;

select materia, industrias, count(*)/(select count(*) from financieras) as Probabilidad from financieras where materia in(select distinct materia from financieras) and industrias in(select distinct industrias from financieras) group by industrias, materia order by materia, industrias;