unique together
Date: March 25th 2016
Last updated: March 25th 2016
unique_together is an option that can be added to a model in models.py. unique_together is executed at the database-level so it requires a suitable backend to work. I have tried it with MySQL and it works. The main premise is to pass a tuple of tuples containing the fields that must be unique in the table (model).
In this example I wanted to restrict a database table containing surfboards from receiving duplicate entries. Only the major differences are distinguished.
models.py
class Board(models.Model):
SQUASH = 'SQH'
SQUARE = 'SQE'
ROUNDED = 'ROU'
TAIL = ((SQUASH, 'Squash'),
(SQUARE, 'Square'),
(ROUNDED, 'Rounded'),
#<- snipped ->
boardtail = models.CharField('Tail shape', max_length=3, choices=TAIL)
boardlength = models.DecimalField('Length', max_digits=4, decimal_places=2)
boardwidth = models.DecimalField('Width', max_digits=4,
decimal_places=2, null=True, blank=True)
boardmake = models.CharField('Make', max_length=20)
#<- snipped ->
def __str__(self):
return '{} {}'.format(self.boardlength, self.boardmake)
###################### solution ########################
# Note that this failed when passing only one set of tuples
class Meta:
unique_together = (('boardtail', 'boardlength',
'boardmake', 'boardwidth'))
########################################################
