Django Many-to-Many data model

Question

I'm trying to create a data structure that involves Products, Customers and Orders. Customers and Products are independent tables, while the Orders references Products and Customers.

Orders table fields:

Time stamp
Customer
Product along with Quantity

Here is my attempt at creating a django model to achieve this:

from django.db import models

class Customer(models.Model):
    name = models.CharField(max_length=30)
    latitude = models.FloatField(default=0)
    longitude = models.FloatField(default=0)

class Product(models.Model):
    name = models.CharField(max_length=30)
    weight = models.FloatField(default=0)

class Order(models.Model):
    customer = models.ForeignKey(Customer, on_delete=models.CASCADE)
    timestamp = models.DateTimeField(auto_now=True)
    products = models.ManyToManyField(Product)
    quantity = ?

How do I create a quantity field that maps to a particular product? Alternate models to achieve the same results are also welcome.

For those looking for how to use this model in django admin, this should help: stackoverflow.com/questions/6034047/… — NFern
– NFern, Commented Aug 21, 2017 at 3:36

D.Nibon · Accepted Answer · 2017-08-05 08:57:21Z

2

Use through in your ManyToManyField.

from django.db import models

class Customer(models.Model):
    name = models.CharField(max_length=30)
    latitude = models.FloatField(default=0)
    longitude = models.FloatField(default=0)

class Product(models.Model):
    name = models.CharField(max_length=30)
    weight = models.FloatField(default=0)

class Order(models.Model):
    customer = models.ForeignKey(Customer, on_delete=models.CASCADE)
    timestamp = models.DateTimeField(auto_now=True)
    line_items = models.ManyToManyField(Product, through='OrderItem')

class OrderItem(models.Model):
    product = models.ForeignKey(Product)
    order = models.ForeignKey(Order)
    quantity, price, discount, ...

answered Aug 5, 2017 at 8:57

D.Nibon

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Comments

Arpit Solanki · Accepted Answer · 2017-08-05 05:23:01Z

0

I would suggest a model which contain a product and its quantity in an order. Something like below.

class ProductOrder(models.Model):
    product = models.ForeignKey(Product)
    quantity = models.IntegerField()

Then in order:

class Order(models.Model):
    customer = models.ForeignKey(Customer, on_delete=models.CASCADE)
    timestamp = models.DateTimeField(auto_now=True)
    products = models.ManyToManyField(ProductOrder)

answered Aug 5, 2017 at 5:23

Arpit Solanki

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1 Comment

NFern Over a year ago

Thank you, this was in the correct direction. What worked for me is the "through ="

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