List Data from Multiple Models in Single HTML Table

Question

I am trying to render data from 3 models in single html table. I have tried an error few times but failed. Below is my code. The workstation, printer and laptop have foreign of site ID. I want to list all the workstation, laptop and printer filter by a site.

Below is my code:

Models:

class Site(models.Model):
    site_name = models.CharField(max_length=30, blank=True, null=True, verbose_name="Site Name")
    site_address = models.CharField(max_length=30, blank=True, null=True, verbose_name="Site Address")

    def __str__(self):
        return self.site_name

class Workstation(models.Model):
    name = models.CharField(max_length=30, blank=True, null=True, verbose_name="Workstation Name")
    serial = models.CharField(max_length=30, blank=True, null=True, verbose_name="Serial")
    workstation_model = models.CharField(max_length=30, blank=True, null=True, verbose_name="Workstation Model")
    sitename = models.ForeignKey(Site, on_delete=models.SET_NULL, blank=True, null=True, verbose_name="Site")

    def __str__(self):
        return self.name
    
class Laptop(models.Model):
    name = models.CharField(max_length=30, blank=True, null=True, verbose_name="Laptop Name")
    serial = models.CharField(max_length=30, blank=True, null=True, verbose_name="Serial")
    laptop_model = models.CharField(max_length=30, blank=True, null=True, verbose_name="Laptop Model")
    sitename = models.ForeignKey(Site, on_delete=models.SET_NULL, blank=True, null=True, verbose_name="Site")

    def __str__(self):
        return self.name
    
class Printer(models.Model):
    name = models.CharField(max_length=30, blank=True, null=True, verbose_name="Printer Name")
    serial = models.CharField(max_length=30, blank=True, null=True, verbose_name="Serial")
    printer_model = models.CharField(max_length=30, blank=True, null=True, verbose_name="Printer Model")
    sitename = models.ForeignKey(Site, on_delete=models.SET_NULL, blank=True, null=True, verbose_name="Site")

    def __str__(self):
        return self.name

URL:
urlpatterns = [
    path('', views.SiteView.as_view(), name='site'),
    path('report/<sitename>', views.ReportView.as_view(), name='reportview'),
]

Template 1: Site List

    <table>
        <tr>
          <th>Site</th>
          <th>Address</th>
        </tr>
        {% for site in site_list %}
        <tr>
            <td><a href="{% url 'reportview' site.site_name %}">{{ site.site_name }}</a></td>
            <td>{{ site.site_address }}</td>
        </tr>
        {% endfor %}
       </table>

Template 2: Report equipment by site

   <table>
        <tr>
          <th>Device</th>
          <th>Serial</th>
        </tr>
        {% for item in site %}
        <tr>
            <td>{{ item.name }}</td>
            <td>{{ item.serial }}</td>
        </tr>
        {% endfor %}
       </table>

View for template 1: Successful output:

class SiteView(ListView):
    model = Site
    template_name = "mytestapp/site.html"

View for template 2: Failed
class ReportView(TemplateView):
    template_name = "mytestapp/report.html"

    def post(self, request):
        site = request.POST["site"]
        context = super().get_context_data(request)
        context["site"] = Workstation.objects.get(sitename=site)
        context["site"] = Laptop.objects.get(sitename=site)
        context["site"] = Printer.objects.get(sitename=site)
        return context

I am trying to list workstation, laptop and printer in single table filter by a site. Sample output: image

Sample output

Answer 1

You are essentially looking for a union, filter all three models by sitename then union them together. Make sure to change in sitename according to your requirements.

# Here we loop over the three models and add the subqueries to the query list
queries = []
for model in [Printer, Laptop, Workstation]:
    queries.append(
        model.objects.filter(sitename=1) 
        .values("name", "serial")
    )
# We are unpacking the previously added queries, p stands for printer, same for l and w
p, l, w = queries
print(p)
# Here we are doing union of the three models,i.e
# Printer union Laptop union Workstation
plw = p.union(l, w, all=True)

<QuerySet [{'name': 'Epson', 'serial': '2'}, {'name': 'printer1', 'serial': '23'}, {'name': 'Asus', 'serial': '1'}, {'name': 'Dell', 'serial': '56'}, {'name': 'Tas', 'serial': '1'}, {'name': 'WS2', 'serial': '234'}]>

Django doesn't give much control in union queries so you might want to use raw queries if you need more control. Or you can query all 3 models separately and chain them together using itertools.chain

from itertools import chain
print(list(chain(*queries)))

Views

class ReportView(TemplateView):
    template_name = "mytestapp/report.html"

    def get_context_data(self, *args, **kwargs):
        context = super().get_context_data(*args, **kwargs)
        site = kwargs["sitename"]
        queries = []
        for model in [Printer, Laptop, Workstation]:
            queries.append(model.objects.filter(sitename=site).values("name", "serial"))
        p, l, w = queries
        print(p)
        plw = p.union(l, w, all=True)
        context["site"] = plw
        return context

The url should look like this http://127.0.0.1:8000/report/1