MySQL - Eliminar en MYSQL

create table Profesor(

idProf varchar(5),

 Nombre varchar(30),

 Grado varchar(20),

 Sueldo integer,

 PRIMARY KEY (idProf));

create table Materia(

  idMat varchar(5),

 Nombre varchar(30),

 Creditos integer,

 idProf varchar(5),

 primary key (idMat),

 FOREIGN KEY (idProf) REFERENCES profesor(idProf));

insert into Profesor values("1","Jorge Juarez Molina","Doctorado",20000);

insert into Materia values("01","Español",4,"1");

 insert into Materia values("02","Algebra",5,"2");

DELETE FROM Profesor P

JOIN Materia M

ON M.idProf = P.idProf

GROUP BY Profesor

HAVING count (M.idMat) = 2;

DELETE FROM Profesor WHERE idProf IN (

	select p.idProf

	from Profesor p right JOIN Materia m ON p.idProf=m.idProf

	having count(m.idProf)=2

)

DELETE

    materia.*

FROM

    materia

    INNER JOIN

    (

        SELECT idprof

        FROM materia

        GROUP BY idprof

        HAVING COUNT(*) >= 2

    ) AS a_eliminar ON

            a_eliminar.idprof = materia.idprof;