如何定义两个字段“唯一"作为情侣 [英] How to define two fields "unique" as couple

问题描述

有没有办法在 Django 中将几个字段定义为唯一的?

Is there a way to define a couple of fields as unique in Django?

我有一张(期刊)卷数表，但我不希望同一期刊的卷数超过一个.

I have a table of volumes (of journals) and I don't want more then one volume number for the same journal.

class Volume(models.Model):
    id = models.AutoField(primary_key=True)
    journal_id = models.ForeignKey(Journals, db_column='jid', null=True, verbose_name = "Journal")
    volume_number = models.CharField('Volume Number', max_length=100)
    comments = models.TextField('Comments', max_length=4000, blank=True)

我尝试将 unique = True 作为属性放在 journal_id 和 volume_number 字段中，但它不起作用.

I tried to put unique = True as attribute in the fields journal_id and volume_number but it doesn't work.

推荐答案

有一个简单的解决方案，叫做 unique_together 完全符合您的要求.

There is a simple solution for you called unique_together which does exactly what you want.

例如:

class MyModel(models.Model):
  field1 = models.CharField(max_length=50)
  field2 = models.CharField(max_length=50)

  class Meta:
    unique_together = ('field1', 'field2',)

就你而言:

class Volume(models.Model):
  id = models.AutoField(primary_key=True)
  journal_id = models.ForeignKey(Journals, db_column='jid', null=True, verbose_name = "Journal")
  volume_number = models.CharField('Volume Number', max_length=100)
  comments = models.TextField('Comments', max_length=4000, blank=True)

  class Meta:
    unique_together = ('journal_id', 'volume_number',)

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