[haron]

prueba con esto a ver si te sirve:

      SELECT  count(DISTINCT ex.doc_numero)
      FROM    expalu  ex
      WHERE  "condiciones" and exists

                                  (SELECT  null
                                   FROM   insren as ins
                                   WHERE ins.doc_numero=ex.doc_numero AND ins.carrera=ex.carrera
                                   AND "condiones"
                                   Group By ins.doc_numero,ins.carrera
                                    HAVING 6<= count(DISTINCT cod_ren) and count(DISTINCT cod_ren) <=10)