Uso de Instruccion AS para crear campo en SQL

[[Caral]]

Hola
La verdad no lo entiendo bien, tal vez asi:

Código SQL [-]
select alumno.alumno_apellido, alumno.alumno_nombre,
(select infxmateria.ixm_nota from infxmateria where infxmateria.ixm_idmateria = 1 and ixm_idciclolectivo = 2008 and
ixm_idalumno = alumno.alumno_idalumno and ixm_idinforme = 1) as matematica1
from alumno join alumxcurso on (alumno.alumno_idalumno = alumxcurso.axc_idalumno)where alumxcurso.axc_idcurso = 1 and alumxcurso.axc_iddivision = 'A' and alumxcurso.axc_idciclolectivo = 2008 order by alumno.alumno_apellido

Saludos