Django version 1.10

class Game(models.Model): game_code = models.CharField(max_length=10) home_team = models.ForeignKey(Team, related_name="home_set", default=2, blank=True, null=True) away_team = models.ForeignKey(Team, related_name="away_set", default=2, blank=True, null=True) class GameCoefficient(models.Model): game = models.ForeignKey(Game, default=3) win_type = models.CharField(choices=win_type, max_length=250, blank=True, null=True, default="") value = models.FloatField(max_length=250, blank=True, null=True, default="") class BaseView(View): data = dict() template = "index.html" def get(self, request): self.data['coefficents_and_game'] = GameCoefficient.objects.all().select_related('game') return render_to_response(self.template, self.data)

When rendering, I get a GameCoefficient and a ForeignKey GAME while the template gets the GameCoefficient model and if I do

 {% for item in coefficents_and_game %} {{item.game}} {% endfor %}

In this case, the game code (game_code) is repeated by the number of GameCoefficient, and I need ONE request to display Game and GameCoefficient. But according to the Game table, the associated GameCoefficient table.

 {% for game in coefficents_and_game %} {{game.game_code}} {% for coefficient in game %} {{coefficient.win_type}} {{coefficient.value}} {% endfor %} {% endfor %}

By reading this, you can make one of these "select_related" statements, "fetch_reverse_relations", "prefetch_related", but I couldn’t fully understand the difference between them in order to achieve the result and output the query example in reverse order.

    1 answer 1

    select_related should be used for the querisset model in which the ForeingKey is ForeingKey , i.e. in connection many to one, on the side of many. prefetch_related works the other way round, on the side of one pulls all the related objects, it can also be used for connecting many to many.

     Team.objects.prefetch_related('home_set') Game.objects.select_related('home_team')

    Both of these methods can be used to capture links of related models.
    In your case, to capture all 3 tables, you can use the following querisset:

     self.data['coefficents_and_game'] = GameCoefficient.objects.select_related('game__home_team', 'game__away_team')

    So they can be accessed in the template:

     {% for game in coefficents_and_game %} {{ game.win_type }} {{ game.value }} {% for coefficient in game.game %} {{ coefficient.game_code }} # Можно добавить еще один внутренний цикл # по ключам home_team и away_team {% endfor %} {% endfor %}