Combine the information of two tables into a single Django model - django

Question

I need to read data for an external database (I cannot modify the table structure) with the two following tables:
Table1
Key (primary key)
Field1
Table2
Key (primary key)
Field2
Is it possible to combine these two tables into a single Django Model that looks like:
Model:
Key (primary key)
Field1
Field2
Additional information:
The keys of the entries in Table2 are a subset of the entries in Table1. So for any entry in Table2 there is a matching entry in Table1, but not viceversa
Work so far:
I have a one model for each table (1 and 2) and Table1 model has a "field2" #property that looks up the corresponding information in the Table2 model.
Also, I can do this at the sql level with the following query:
SELECT
table1.key,
table1.field1,
table2.field2,
FROM
table1
LEFT OUTER JOIN table2
ON table1.key=table2.key
ORDER BY table1.key ASC
===
Solution implementation details update after seeing some of the answers:
From Daniel Roseman's answer
I ended up with two models:
class Model1(models.Model):
key = models.CharField(max_length=100, primary_key=True)
field1 = models.TextField()
class Meta:
managed = False
db_table = 'Table1'
def field2_value(self):
try:
return self.field2.value
except Model2.DoesNotExist:
return None
class Model2(models.Model):
key = models.OneToOneField(Model1, primary_key=True, db_column='key',
related_name='field2')
field2 = models.TextField()
class Meta:
managed = False
db_table = 'Table2'
While it is not exactly what I had originally in mind when I asked this question, it meets my desired use case
Also, here are the corresponding admin classes:
class Model2Admin(admin.StackedInline):
model = Model2
#admin.register(Model1)
class Model1Admin(admin.ModelAdmin):
inlines = (Model2Admin,)
list_display = ('key', 'field1', 'field2_value')
# Loads the related property in one SQL call instead of one call per entry
list_select_related = ('field2',)
Thanks KaaN SARIKAYA for your great answer. I didn't know that I could create a view of the two tables. If I could modify the database structure I would opt for your option.

Answer 1

A better solution would be to keep these as two models, but have the primary key of the second be a OneToOneField to the first.

Answer 2

You cannot merge the model because they are 2 physical tables, django models are tied by the database table names so you couldn't do what you want. If you have the control for those external database tables and have the right to modify them, you should modify the schema first and merge the data. If you don't want to or you cannot modify anything, your current way is OK.

Answer 3

You can create a table_view on sql and make an abstract model on django . Suppose you have 2 pyhsical models and tables.
SQL CODE:
CREATE OR REPLACE VIEW combine_two_model_view AS
SELECT
mt1.name as mt1_name,
mt2.name as mt2_name,
mt1.pub_date as mt1_pub_date
.
.
.
.
FROM modeltable1 mt1
LEFT JOIN modeltable2 mt2 ON mt2.id = mt1.id
ALTER TABLE combine_two_model_view
OWNER TO dbuser;
we created sql view table. now, we will create an abstract model
in your models.py:
class YourModelsCombine(models.Model):
class Meta:
abstract = True
db_table = "combine_two_model_view"
mt1_name = models.CharField(max_length=100)
mt2_name = models.TextField(max_length=2000)
mt1_pub_date = models.DateTimeField("Publish Date", auto_now_add=True)
mt2_pub_date = models.DateField("Updated Date", auto_now=True)
mt1_integer = models.IntegerField(default=0)
#etc
attention: make sure your table view variable names and model variable names must be same. Finally;
in your admin.py:
admin.site.register(YourModelsCombine)
You will see combine of two tables on your django-admin
I hope this helps to you