Question

Django中是否有可能创建一个查询，该查询将使用两个ForeignKey在表之间创建联接？

为了说明我的意思，假设我在Django中具有以下模型：

class Author(models.Model):
     name = models.TextField()

class Publisher(models.Model):
     name = models.TextField()

class BooksSold(models.Model):
     author = ForeignKey(Author, related_name='books_sold')
     publisher = ForeignKey(Publisher, related_name='books_sold')
     books_sold = models.IntegerField()

class BooksPrinted(models.Model):
     author = ForeignKey(Author, related_name='books_printed')
     publisher = ForeignKey(Publisher, related_name='books_printed')
     books_printed = models.IntegerField()

我想使用Author和Publisher键联接BooksSold和BooksPrinted表。在sql中将是：

SELECT A.author_id
      ,A.publisher_id
      ,A.books_sold
      ,B.books_printed 
FROM table_books_sold A INNER JOIN table_books_printed 
ON A.author_id = B.author_id AND 
   A.publisher_id = B.publisher_id

我当前使用的方法是遍历其中一个通过ForeignKey加入的模型，并使用另一个ForeignKey进行过滤，对于此示例：

   def get_books_printed(books_sold_model):
       return next(b for b in books_sold_model.author.books_printed if b.publisher_id = books_sold_model.publisher_id

   books_sold_models = BooksSold.objects.all().prefetch(author__books_printed)
   for book_sold_model in books_sold_models:
       books_printed = get_books_printed(books_sold_model)

我想知道是否有一种方法可以避免遍历所有实例，直到找到与其他ForeignKey的匹配项为止

通过2个ForeignKeys在django中加入模型

0 个答案: