django外键三种多对多关系表的创建

Posted 2021-06-03 不想拖累他人

三种 全自动 半自动 纯手动

全自动

以图书和作者为例

class Book(model.Model):
    title = model.CharField(max_length=32)
    authors = model.ManyToManyField(to=\'Author\')


class Author(model.Model):
    name = model.CharField(max_length=32)
 

纯手动

class Book(model.Model):
    title = model.CharField(max_length = 32)


class Author(model.Model):
    name = model.CharField(max_length = 32)



class Book2Author(model.Model):
    book = model.ForeignKey(to=\'Book\'，on_delete=models.CASCADE)
    author = model.ForeignKey(to=\'Author\'，on_delete=models.CASCADE)

半自动

class Book(model.Model):
    title = model.CharField(max_length=32)
    author = model.ManyToManyField(to=\'Author\',through=\'Book2Author\',though_fields = (\'book\',\'author\'))
        


class Author(model.Model):
    name = model.CharField(max_length=32)


class Book2Author(model.Model):
     book = model.ForeignKey(to=\'Book\'，on_delete=models.CASCADE)
     author = model.ForeignKey(to=\'Author\'，on_delete=models.CASCADE)

半自动相对使用较多 有好的扩展性且可以使用orm查询

建立外键时要添加on_delete参数 1.x版本会默认级联删除，之后的版本都需额外填写否则会报错