Merge 2 models (tables) in Django and show it in my template - django

Question

I have 2 models one defines all the all the devices that I have, and the other stores the information that the devices are obtaining. The code of they is the following,
class Device(models.Model):
dev_eui = models.CharField(max_length=16, primary_key=True)
producer = models.CharField(max_length=20, blank=True, null=True)
model = models.CharField(max_length=20, blank=True, null=True)
firmware = models.CharField(max_length=10, blank=True, null=True)
dev_name = models.CharField(max_length=20, blank=True, null=True)
description = models.CharField(max_length=40, blank=True, null=True)
fixed = models.BooleanField()
dev_lat = models.FloatField(null=True, blank=True)
dev_lon = models.FloatField(null=True, blank=True)
deco_name = models.CharField(max_length=20)
fleet_id = models.IntegerField(null=True, blank=True)
class DevData(models.Model):
data_uuid = models.UUIDField(primary_key=True, default=uuid.uuid1, editable=False)
data_id = models.IntegerField()
dev_eui = models.CharField(max_length=16)
gateway = models.CharField(max_length=25)
data_timestamp = models.DateTimeField()
rssi = models.IntegerField()
snr = models.IntegerField()
datarate = models.CharField(max_length=15)
frequency = models.IntegerField()
seq = models.IntegerField()
data_1 = models.FloatField()
data_2 = models.FloatField(null=True, blank=True)
data_3 = models.FloatField(null=True, blank=True)
data_4 = models.FloatField(null=True, blank=True)
data_5 = models.FloatField(null=True, blank=True)
data_6 = models.FloatField(null=True, blank=True)
data_7 = models.FloatField(null=True, blank=True)
Actually what I want is show a table in my template, combining all the data from devData and adding the dev_name and fleet_id from devices.
Now what I'm doing is obtaining all the data and in the template filtering it. But I'm sure it's better and easier doing this in the views.py, but I don't know how.
Reading some info, I found the union() function but it's not working and I'm not sure if is the best option,
#login_required(login_url='/user_app/login/')
def user_data(request):
dev_data = DevData.objects.all()
devices = Device.objects.all()
test = DevData.objects.all().values_list(
"dev_eui"
).union(
Device.objects.all().values_list(
"dev_eui"
))
ctx = {'DevData':dev_data,'Devices':devices, 'Test':test}
return render(request, template_name='data.html', context=ctx)
This join shows nothing.
Can somebody help me? Thank very much!

Answer 1

You need a foreign key relating the two models.
class Device(models.Model):
dev_eui = models.CharField(max_length=16, primary_key=True)
class DevData(models.Model):
device = models.ForeignKeyField(Device, related_name='dev_data', on_delete=models.CASCADE)
data_uuid = models.UUIDField(primary_key=True, default=uuid.uuid1, editable=False)
data_id = models.IntegerField()
# This is not needed, it can be accessed via instance.device.dev_eui now
# dev_eui = models.CharField(max_length=16)
Then to get all of the DevData instances for a particular device:
for device in Device.objects.all():
x = device.dev_data.all()
Please read the documentation to better understand relationship fields.