ManyToMany表中记录数的简单计数(Simple count of number of records in ManyToMany table)
class Author(models.Model):
name = models.CharField(max_length=100)
age = models.IntegerField()
friends = models.ManyToManyField('self', blank=True)
class Publisher(models.Model):
name = models.CharField(max_length=300)
num_awards = models.IntegerField()
class Book(models.Model):
isbn = models.CharField(max_length=9)
name = models.CharField(max_length=300)
pages = models.IntegerField()
price = models.DecimalField(max_digits=10, decimal_places=2)
rating = models.FloatField()
authors = models.ManyToManyField(Author)
publisher = models.ForeignKey(Publisher)
pubdate = models.DateField()
class Store(models.Model):
name = models.CharField(max_length=300)
books = models.ManyToManyField(Book)
我认为我错过了一些非常明显的东西,但是如何获得在此多对多表中authors = models.ManyToManyField(Author)创建的记录数?
class Author(models.Model): name = models.CharField(max_length=100) age = models.IntegerField() friends = models.ManyToManyField('self', blank=True) class Publisher(models.Model): name = models.CharField(max_length=300) num_awards = models.IntegerField() class Book(models.Model): isbn = models.CharField(max_length=9) name = models.CharField(max_length=300) pages = models.IntegerField() price = models.DecimalField(max_digits=10, decimal_places=2) rating = models.FloatField() authors = models.ManyToManyField(Author) publisher = models.ForeignKey(Publisher) pubdate = models.DateField() class Store(models.Model): name = models.CharField(max_length=300) books = models.ManyToManyField(Book)I think I'm missing something really obvious but how do I get a count for the number of records created in this many-to-many table authors = models.ManyToManyField(Author)?
最满意答案
看看这些文档 ,这很简单:
b = Book.objects.all()[0] b.authors.count()更新:
最初的问题是要求列出数据库中所有作者的列表,而不是查找每本书的作者列表。
要获取数据库中所有作者的列表,请执行以下操作:
Author.objects.count() ## Returns an integer.Check out the docs, it's pretty simple:
b = Book.objects.all()[0] b.authors.count()Update:
The original question was asking for a list of all of the Authors in the database, not looking for a list of authors per book.
To get a list of all of the authors in the database:
Author.objects.count() ## Returns an integer.更多推荐
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