多对多关系中的查询答案

【问题标题】：Query in ManyToMany relation多对多关系中的查询
【发布时间】：2013-11-08 21:49:23
【问题描述】：

我有两个具有多对多关系的模型。代码如下：

class Player(models.Model):
    SEX_CHOICES = (
        ('f', 'Female'),
        ('m', 'Male'),
    )
    tournaments = models.ManyToManyField('Tournament', through = "PlayerTournament",verbose_name = u"Tournament's players")
    first_name = models.CharField(max_length = 30, verbose_name = u"First name")
    last_name = models.CharField(max_length = 50, verbose_name = u"Last name")
    sex = models.CharField(max_length = 1, choices = SEX_CHOICES, default = 'f', verbose_name = u"Sex")
    elo = models.IntegerField(verbose_name = u"ELO")

    class Meta:
        ordering = ['elo']

    def __unicode__(self):
        return "%s - %s" % (self.last_name, self.first_name)

class Tournament(models.Model):
    title = models.CharField(max_length = 100, verbose_name = u"Tournament's title")
    players = models.ManyToManyField('Player', through = "PlayerTournament",verbose_name = u"Tournament's players")
    beginning_date = models.DateTimeField(verbose_name = u"Tournament's beginning", null=True, blank = True)

    def __unicode__(self):
        return self.title

class PlayerTournament(models.Model):
    player = models.ForeignKey(Tournament)
    tournament = models.ForeignKey(Player)

    class Meta:
        db_table ='game_player_tournaments'
        auto_created = Player

我正在尝试进行查询以获取相关字段

PlayerTournament.objects.filter(tournament__title = "Winter").values()

但它不起作用

FieldError: Cannot resolve keyword 'title' into field. Choices are: elo, first, first_name, id, last_name, playertournament, second, sex, statistics, tournament, tournaments

我做错了什么？

【问题讨论】：

标签： python django python-2.7

【解决方案1】：

查看您的模型：

class PlayerTournament(models.Model):
    player = models.ForeignKey(Tournament)
    tournament = models.ForeignKey(Player)

你有 player 和 tournament 互换

你应该这样做：

PlayerTournament.objects.filter(player__title = "Winter").values()

如果您确实在寻找相关领域，您应该使用select_related 或prefetch_related 而不是values（根据您的查询，我非常怀疑）

【讨论】：