How to search the bank with three types of user?

Question

Hello I’m doing a college project, it’s an internship site project, it has to be developed in Java WEB with database. It has three types of user, the student, the company and the administrator. I wonder if there is any way at the time of logging in I do not have to search the three tables.

I was thinking of making a user table, in which you have the email, the password, his type (1-Adm, 2-student...) and finally a field of the user id in your table. Then I would do the query in the user table, and from the type of it, I would discover the table in which it meets and with the id found it.

So I’m doing two searches. there’s another way to do it with just one?

Thank you!

Answer 1

You can join the tables at the time of the query:

select *
from Usuario usu
left join Administrador adm on  adm.id   = usu.id
                            and usu.tipo = 1
left join Aluno alu on  alu.id   = usu.id
                    and usu.tipo = 2

Answer 2

In your User class, set the attribute "Usuario type" or something of the type and when instantiating the object set its type searching the values in an Enum. Sort of like:

public enum TipoUsuario {
    ADMIN, ALUNO, SISTEMA
}

Then when you need to check the type of permission you can refer to the type of permission with a case switch for example:

public static void main(String[] args) {
    Usuario usuario = new Usuario();
    usuario.setNome("Banana");
    usuario.setTipoPermissao(TipoUsuario.ADMIN);

    switch (usuario.getTipoPermissao()) {
    case ADMIN:
        System.out.println("Usuario Administrador.");
        break;
    case ALUNO:
        System.out.println("Usuario Aluno.");
        break;
    case SISTEMA:
        System.out.println("Usuario Sistema.");
        break;
    default:
        System.out.println("Quem diabos é esse cara?");
        break;
    }
}

All this without having to change table structure, when you want to change the type just call the user method.setTipoPermission and change to the type you want.