How to create a django queryset object for inner join?

Question

I have two tables.

class DibbsSpiderDibbsMatchedProductFieldsDuplicate(models.Model):
    nsn = models.TextField()
    nsn2 = models.TextField()
    cage = models.TextField()
    part_number = models.TextField()
    company_name = models.TextField(blank=True, null=True)
    supplier = models.TextField(db_column='Supplier', blank=True, null=True)  # Field name made lowercase.
    cost = models.CharField(db_column='Cost', max_length=15, blank=True, null=True)  # Field name made lowercase.
    list_price = models.CharField(db_column='List_Price', max_length=15, blank=True, null=True)  # Field name made lowercase.
    gsa_price = models.CharField(db_column='GSA_Price', max_length=15, blank=True, null=True)  # Field name made lowercase.
    hash = models.TextField()
    nomenclature = models.TextField()
    technical_documents = models.TextField()
    solicitation = models.CharField(max_length=32)
    status = models.CharField(max_length=16)
    purchase_request = models.TextField()
    issued = models.DateField()
    return_by = models.DateField()
    file = models.TextField()
    vendor_part_number = models.TextField()
    manufacturer_name = models.TextField(blank=True, null=True)
    product_name = models.TextField(blank=True, null=True)
    unit = models.CharField(max_length=15, blank=True, null=True)

    class Meta:
        managed = False
        db_table = 'dibbs_spider_dibbs_matched_product_fields_duplicate'


class DibbsSpiderSolicitation(models.Model):
    line_items = models.IntegerField()
    nsn = models.TextField()
    nomenclature = models.TextField()
    technical_documents = models.TextField()
    purchase_request = models.TextField()

    class Meta:
        managed = False
        db_table = 'dibbs_spider_solicitation'

What will be the equivalent django query for the inner join of two tables on the column nsn? My views function will be like

def inner(request,nsn):
    u_m =  DibbsSpiderDibbsMatchedProductFieldsDuplicate.objects.filter(nsn2__icontains=id)
    c_m = DibbsSpiderSolicitation.objects.filter(nsn__icontains=id)
    obj = .......................
    context = {'obj':obj}
    return render(request,,"a.html",context)

the queryset should return the combination of two tables according to the common nsn.

the obj should return the combination of u_m and c_m. If u_m contains only one rows and c_m contains many rows then the obj must replicate the values of u_m.

score 2 · Answer 1 · answered Jan 03 '22 at 17:49

You can try some of the options:

Adding foreign key constraint and use select_related as per this post
Raw query as mentioned in this stackoverflow post and another post with custom joins

3. Using IN query as per the following logic:

DibbsSpiderDibbsMatchedProductFieldsDuplicate.objects.filter(
        nsn2__in=DibbsSpiderSolicitation.objects.filter(nsn__icontains='text_to_search').values('origin'))

score 2 · Answer 2 · answered Jan 07 '22 at 09:56

First, great model names. Let's alias them: DibbsSpiderDibbsMatchedProductFieldsDuplicate is Apples; DibbsSpiderSolicitation is Oranges

inner_qs = Apples.objects.all().extra(
    tables=("yourapp_oranges",),
    where=("yourapp_apples.nsn=yourapp_oranges.nsn",),
)

The documentation mentions that this api will be deprecated: https://docs.djangoproject.com/en/4.0/ref/models/querysets/#extra

score -1 · Answer 3 · answered Jan 01 '22 at 17:53

Option #1 - Introduce a ForeignKey (Recommended):

Under the class DibbsSpiderDibbsMatchedProductFieldsDuplicate add:

fkey = models.ForeignKey('DibbsSpiderSolicitation')

then you can easily access their join:

obj = DibbsSpiderDibbsMatchedProductFieldsDuplicate.Objects.filter(fkey__nsn).select_related()

Now it is your choice what you wish to do with nsn2

Option #2 - without a ForeigKey:

Raw SQL:

obj = DibbsSpiderDibbsMatchedProductFieldsDuplicate.objects.extra(where = ['''SELECT *
FROM DibbsSpiderSolicitation
INNER JOIN DibbsSpiderDibbsMatchedProductFieldsDuplicate
ON DibbsSpiderSolicitation.nsn = DibbsSpiderDibbsMatchedProductFieldsDuplicate.nsn2;'''])
# or
obj = DibbsSpiderDibbsMatchedProductFieldsDuplicate.objects.raw('''SELECT *
FROM DibbsSpiderSolicitation
INNER JOIN DibbsSpiderDibbsMatchedProductFieldsDuplicate
ON DibbsSpiderSolicitation.nsn = DibbsSpiderDibbsMatchedProductFieldsDuplicate.nsn2;''')

Using filter:

obj = DibbsSpiderSolicitation.objects.filter(nsn__in=DibbsSpiderDibbsMatchedProductFieldsDuplicate.objects.nsn2)

Sorry, I was not able to test any.

How to create a django queryset object for inner join?

3 Answers3

Option #1 - Introduce a ForeignKey (Recommended):

Option #2 - without a ForeigKey:

Raw SQL:

Using filter: