join two tables in django admin to get columns for display_list

Question

I am having problem with list_display/joining two table for django admin interface.

I want to have columns- program_name and is_active from SchPrograms model with parameter_name, parameter_description from VisVisitParameters model in django admin. I am able to have those columns which i am using with return in each of these models. I tried to take help from the question that already has been asked. But still i could not able to figured this out.

class SchPrograms(models.Model):
  program_id = models.AutoField(primary_key=True)
  program_name = models.CharField(max_length=200, blank=True, null=True)
  creation_timestamp = models.DateTimeField(blank=True, null=True)
  is_active = models.IntegerField()

  class Meta:
      managed = True
      db_table = 'sch_programs'
      app_label = 'polls'

  def __str__(self):
      return self.program_name

class VisVisitParameters(models.Model):
   vparameter_id = models.AutoField(primary_key=True)
   parameter_name = models.CharField(max_length=300, blank=True, null=True)
   parameter_description = models.TextField(blank=True, null=True)
   is_active = models.IntegerField(choices=STATUS_CHOICES)

   class Meta:
       managed = False
       db_table = 'vis_visit_parameters'

   def __str__(self):
       return str(self.vparameter_id)
       app_label = 'polls'


class VisVisitParameterMappings(models.Model):
    vp_map_id = models.AutoField(primary_key=True)
    vparameter =  models.ForeignKey(VisVisitParameters,on_delete=models.CASCADE)
    program = models.ForeignKey(SchPrograms,on_delete=models.CASCADE)
    display_order = models.IntegerField(blank=True, null=True)
    is_active = models.IntegerField()

    class Meta:
       managed = False
       db_table = 'vis_visit_parameter_mappings'
       app_label = 'polls'

    def __str__(self):
       return str(self.parameter_name)

model.py

class VisVisitParameterMappings_admin(admin.ModelAdmin):
    list_display =   ('program_name','is_active','parameter_name','parameter_description ')

Answer 1

To display the required items on the list display page you can write your custom methods, as documented here.

For example, for your field named program_name you can have:

def program_name(self, obj):
    if obj.program:
        return obj.program.program_name

program_name.short_description = 'Program name'

and for another model field named parameter_name , you may have:

def parameter_name(self, obj):
    if obj.vparameter:
        return obj.vparameter.parameter_name

parameter_name.short_description = 'Parameter Name'

Hope it helps.