Re: Django Model | Relationship question. Student->School Class

On Tue, Dec 22, 2015 at 6:50 AM, Pemby <briandanielz@gmail.com> wrote:
> With this code for example.
>
> class Students(models.Model):
> first_name = models.CharField(max_length=30)
> last_name = models.CharField(max_length=30)
> classChoice1 = ?
> classChoice2 = ?
> classChouce3 = ?
>
> class Class(models.Model):
> class_name = models.CharField(max_length=30)
> class_discription = models.CharField(max_length=30)
>
>
> Say for example I have Nth students, S1 S2 S3 ... and Nth classes (as in
> college class) C1 C2 C3 ...
> And I want to create a relationship where each student can only be assigned
> to one class uniquely for each classChoice
> selected. How would I create that relationship?

Remove the classChoiceN fields from Students, and add a ManyToMany
between Student and Class (remember model class names should be
singular, so "Student", not "Students") using a through table with an
additional "choice" integer field.

The "choice" field should have a maximum value of 3, and you will want
unique_together constraints on the through table for (student, class)
and (student, choice) - you can't sign up for the same class twice,
and you can only have one of each choice.

Cheers

Tom

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