Procedures MYSQL - Pass parameters or not

Question

I created a procedure to make the following process: If you do not enter the required parameter, you will bring the complete list of what I want (in this case a list of students etc). If you type, it will bring the specific student. But instead, she only brings it back if I type the id of the student, ignoring the condition IF P_idAluno IS NULL THEN.

 BEGIN IF (P_idAluno IS NULL)
  THEN SELECT A.idAluno AS CodigoAluno,
  A.NomeAluno AS Nome, A.SexoAluno AS Sexo, A.DataNascimento, T.Turma,
  S.Serie, T.Turno 
  FROM tbAluno A 
  INNER JOIN tbTurma T ON T.idTurma = A.id_Turma 
  INNER JOIN tbSerie S ON S.idSerie = T.id_Serie 
  ORDER BY A.NomeAluno; 
 ELSE 
  SELECT A.idAluno AS CodigoAluno, A.NomeAluno AS
  Nome, A.SexoAluno AS Sexo, A.DataNascimento, T.Turma, S.Serie, T.Turno
  FROM tbAluno A 
  INNER JOIN tbTurma T ON T.idTurma = A.id_Turma
  INNER JOIN tbSerie S ON S.idSerie = T.id_Serie WHERE idAluno = P_idAluno;
 END IF;
END

Answer 1

Easiest way to do it is like this:

    BEGIN 

      SELECT A.idAluno AS CodigoAluno, A.NomeAluno AS
      Nome, A.SexoAluno AS Sexo, A.DataNascimento, T.Turma, S.Serie, T.Turno
      FROM tbAluno A 
      INNER JOIN tbTurma T ON T.idTurma = A.id_Turma
      INNER JOIN tbSerie S ON S.idSerie = T.id_Serie WHERE idAluno = COALESCE(P_idAluno,A.idAluno);

    END;