title: Error Code 1241 - Operand should contain 1 column(s)
body: <p>I was creating a procedure and I came across this.
  Does anyone know how to solve this?</p>
  
  <pre><code>delimiter $$
  create procedure sp_cadastraAluno(
  in nome varchar(150),
  in chamada varchar(3),
  in data date, 
  in ra varchar(12),
  in turma varchar(50),
  in cpf varchar(14))
  begin
      declare x int;
      set x = (select * from tb_coordenador inner join tb_professor
      on tb_coordenador.cd_coord = tb_professor.cd_coord
      inner join prof_turma on
      tb_professor.cd_prof = prof_turma.cd_prof
      inner join tb_turma on
      prof_turma.cd_turma = tb_turma.cd_turma 
      inner join tb_aluno on
      tb_turma.cd_turma = tb_aluno.cd_turma where nm_turma = turma and tb_professor.cd_cpf = cpf);
  
      insert into tb_aluno(nm_aluno, cd_chamada, dt_nascimento, cd_ra, cd_turma) values
      (nome, chamada, data, ra, x);
  end $$
  </code></pre>
  
  <p>I need to insert in <code>tb_aluno</code> and for this, I need to pull the code already inserted in <code>tb_turma</code>, but this error appears.</p>