title: How to make an Inner Join in django without foreign key?
body: <p>how to make statement of join on in django 1.11,
  i want to create this statement :</p>
  
  <pre><code>select t1.name ,t2.str, t2.num
  from table_1 as t1
  join table_2 as t2 on t2.product_id = t1.id and t2.section_num = 2;
  
  the models:
  
  
  class t1(UTModelTS):
      alt_keys = product_alt_keys
      name = utCharField()
      ...
  
  class t2(UTModelTS):
      alt_keys= [('pr_id', 'section')]    
      str = utCharField()
      num = models.IntegerField()
  
      ...
  </code></pre>
  
  <p>i tried </p>
  
  <pre><code> t1 = t1.objects.filter(**params).exclude(**exclude)
   t1 = t1.select_related('t2')
  `
  </code></pre>
  
  <p>but this make no sense since acoridng to django doc :
  <strong>select_related
  Returns a QuerySet that will “follow” foreign-key relationships...</strong>
  from <a href="https://docs.djangoproject.com/en/2.2/ref/models/querysets/" rel="nofollow noreferrer">https://docs.djangoproject.com/en/2.2/ref/models/querysets/</a> .</p>