Multiple tuples in unique_together
Each tuple results in a discrete UNIQUE clause being added to the CREATE TABLE query. As such, each tuple is independent and an insert will fail if any data integrity constraint is violated.
When I am defining a model and using unique_together in the Meta, I can define more than one tuple. Are these going to be ORed or ANDed? That is lets say I have a model where

class MyModel(models.Model):
    druggie = ForeignKey('druggie', null=True)
    drunk = ForeignKey('drunk', null=True)
    quarts = IntegerField(null=True)
    ounces = IntegerField(null=True)

    class Meta:
        unique_together = (('drunk', 'quarts'),
                           ('druggie', 'ounces'))

either both druggie and ounces are unique or both drunk and quarts are unique, but not both.