How can i query with ManyToManyField?

Question

If i know company_id, how can i call a query list department, each department have list user and each user has username and staff_id? Example models and output below

class User(models.Model):
    username=models.CharField(max_length=40,unique=True)

class Company(models.Model)
    name=models.CharField(max_length=100)
    users = models.ManyToManyField('User', through='User_Company',related_name="companies")

class Department(models.Model)
    name=models.CharField(max_length=100)
    users = models.ManyToManyField('User', through='User_Department',related_name="departments")

class User_Department(models.Model)
    user = models.ForeignKey('User', on_delete=models.CASCADE,related_name="ud_membership")
    department = models.ForeignKey('Department', on_delete=models.CASCADE,related_name="ud_membership")

class User_Company(models.Model)
    user = models.ForeignKey('User', on_delete=models.CASCADE,related_name="uc_membership")
    company = models.ForeignKey('Company', on_delete=models.CASCADE,related_name="uc_membership")
    staff_id = =models.CharField(max_length=50)

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I want data output with this format:

Answer 1

You can find the departments that have at least one useer in common with:

Department.objects.filter().

The .distinct() clause [Django-doc] will prevent returing the Department s multiple times. Without .distinct() , each Department will be returned that many times as there are common users.