CODEWITHSUNDEEP
django-models
Ali Raza Javeed
Ali Raza Javeed

Reputation: 155

multiple foreign keys in intermediate table of same table DJANGO

In many to many relationships with the intermediate table, I use multiple foreign keys. but got error like The model is used as an intermediate model by 'examples.Employee.designation', but it has more than one foreign key from 'Employee', which is ambiguous. You must specify which foreign key Django should use via the through_fields keyword argument my models are with intermediate table

class Employee(models.Model):
    code = models.CharField(max_length = 256)
    designation =models.ManyToManyField(Designation,related_name='+',through = 'HRManagement',blank=True)
    status = models.BooleanField(default = True)
    join_date = models.DateField(default=datetime.datetime.now)
    leave_date = models.DateField(blank = True, null=True)
    username = models.CharField(max_length = 256)
    password = models.CharField(max_length = 256)
    first_name = models.CharField(max_length = 256)
    last_name = models.CharField(max_length = 256)
    address = models.TextField()

class Designation(models.Model):
    name = models.CharField(max_length = 256)

class HRManagement(models.Model):
    employee = models.ForeignKey(Employee, related_name = 'employee', null=True,on_delete=models.CASCADE)
    designation = models.ForeignKey(Designation, on_delete=models.CASCADE,default=None,null=True)
    reportto = models.ForeignKey(Employee, null=True, related_name='reportto',on_delete=models.CASCADE)

how could I fix this error? please help me in models building

Upvotes: 2

Views: 954

Answers (1)

Jake F
Jake F

Reputation: 131

The through model (HRManagement) contains two ForeignKeys to the same model (Employee being linked to by both employee and reportto), which is ambiguous. This is what through_fields is for.

Try adding through_fields=('employee', 'designation') to designation so that the field is declared as:

designation = models.ManyToManyField(Designation, related_name='+', through='HRManagement', blank=True, through_fields=('employee', 'designation'))

As a different answer in a different question points out, the order of the fields in through_fields is (source, destination). If swapped, makemigrations errors out with E339.

Upvotes: 3

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