CODEWITHSUNDEEP
pythondjangodjango-models
DauleDK
DauleDK

Reputation: 3443

Multiple ForeignKey to the same field in Django

I can't add two foreign key constraints to the same field?

I am not 100% sure about the relationship, so I have included the tables. Hope it can help others with learning Django as well: Transaction

+----------+-----+---------------------+
|   guid   | plu |      datetime       |
+----------+-----+---------------------+
| 00003516 |   1 | 2015-09-22 12:11:12 |
| 0000386a |   2 | 2015-02-22 12:11:10 |
| 0000c59d |   2 | 2015-03-22 12:11:10 |
| 0000f03f |   3 | 2015-01-22 12:12:12 |
+----------+-----+---------------------+

Plu

+-----+------+
| plu | name |
+-----+------+
|   1 | aaa  |
|   2 | bbb  |
|   3 | ccc  |
+-----+------+

Finance

+-----+------------+------------+-------+
| plu |    from    |     to     | price |
+-----+------------+------------+-------+
|   1 | 2013-01-22 | 2015-01-23 |    10 |
|   1 | 2015-01-23 | 2015-02-29 |    20 |
|   2 | 2013-01-22 | 2015-01-22 |    10 |
|   3 | 2013-01-22 | 2015-01-22 |    30 |
+-----+------------+------------+-------+

Based on this I have created the following models: Finance

class Finance(models.Model):
    guid = models.AutoField(primary_key=True)
    from = models.DateField()
    to = models.DateField()
    price = models.DecimalField(max_digits=10, decimal_places=2)

PLU

class Plu(models.Model):
    plu = models.IntegerField(primary_key=True)
    name = models.CharField(max_length=200, null=True)

Transaction

class Transaction(models.Model):
    guid = models.CharField(primary_key=True, max_length=38)
    plu = models.ForeignKey(Plu, db_column='plu')
    finance = models.ForeignKey(Finance, db_column='plu')
    datetime = models.DateTimeField()

When I try to run this i get the following error - what to do?: 

app.Transaction: (models.E007) Field 'finance' has column name 'plu' that is used by another field.
    HINT: Specify a 'db_column' for the field.

Upvotes: 1

Views: 1117

Answers (1)

Sayse
Sayse

Reputation: 43330

You've copy and pasted and included the same db_column name, you need to change it

finance = models.ForeignKey(Finance, db_column='finance')

Note: You don't actually need the db_column specified at all since you're just setting it to the name of the field anyway

finance = models.ForeignKey(Finance)

Upvotes: 1

Related Questions