select count(des_con.id_alu) tl_des,alumno.nom_per, alumno.ape_per, curso.des_cur
from des_con 
inner join alumno on alumno.id_alu = des_con.id_alu 
inner join alumcurso on alumcurso.id_alu = alumno.id_alu
inner join curso on curso.cod_cur= alumcurso.cod_cur
where alumno.est_alu='h'
group by des_con.id_alu
order by tl_des desc, des_cur, des_con.id_alu