Djangoの django.db.migrations.operations.AlterUniqueTogether をわかりやすく解説！

What is AlterUniqueTogether?

AlterUniqueTogether is a Django migration operation that is used to modify the unique_together constraint on a model's Meta class. The unique_together constraint ensures that no two instances of a model can have the same combination of values for the specified fields.

When to use AlterUniqueTogether?

You should use AlterUniqueTogether when you need to:

• Add a new unique constraint to a model
• Remove an existing unique constraint from a model
• Change the fields that are included in an existing unique constraint

Syntax of AlterUniqueTogether

The AlterUniqueTogether operation takes two arguments:

• name: The name of the model to modify
• unique_together: A list of tuples, where each tuple specifies the fields that should be included in the unique constraint

Example of AlterUniqueTogether

Here is an example of how to use AlterUniqueTogether to add a new unique constraint to the Author model:

from django.db.migrations import operations

class Migration(migrations.Migration):

    dependencies = [
        ('myapp', '0001_initial'),
    ]

    operations = [
        operations.AlterUniqueTogether(
            name='Author',
            unique_together=[('first_name', 'last_name')],
        ),
    ]

This migration will add a unique constraint to the Author model that ensures that no two authors can have the same first name and last name.

Additional Notes

• The AlterUniqueTogether operation is reversible. This means that you can migrate your database back to the previous state if you need to.
• The AlterUniqueTogether operation will automatically create or drop the appropriate database constraints.
• If you are using a database that does not support unique constraints, the AlterUniqueTogether operation will create indexes instead.

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