class Exam(models.Model):
 category = cached_fields.ForeignKeyField(Category)
 name = models.CharField(max_length=128)
 date = models.DateField()
 created_at = models.DateTimeField(auto_now_add=True)
 updated_at = models.DateTimeField(auto_now=True)

 class Meta:
 unique_together = ('category', 'date')

| insurance_exam | CREATE TABLE `insurance_exam` (
 `id` int(11) NOT NULL AUTO_INCREMENT,
 `name` varchar(128) NOT NULL,
 `date` date NOT NULL,
 `created_at` datetime(6) NOT NULL,
 `updated_at` datetime(6) NOT NULL,
 `category_id` int(11) NOT NULL,
 PRIMARY KEY (`id`),
 UNIQUE KEY `insurance_exam_category_id_a430e581_uniq` (`category_id`,`date`),
 CONSTRAINT `insurance_exam_category_id_a2238260_fk_insurance_category_id` FOREIGN KEY (`category_id`) REFERENCES `insurance_category` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1062 DEFAULT CHARSET=utf8mb4 |

| insurance_exam | CREATE TABLE `insurance_exam` (
 `id` int(11) NOT NULL AUTO_INCREMENT,
 `name` varchar(128) NOT NULL,
 `date` date NOT NULL,
 `created_at` datetime(6) NOT NULL,
 `updated_at` datetime(6) NOT NULL,
 `category_id` int(11) NOT NULL,
 PRIMARY KEY (`id`),
 KEY `category_id` (`category_id`),
 CONSTRAINT `insurance_exam_category_id_a2238260_fk_insurance_category_id` FOREIGN KEY (`category_id`) REFERENCES `insurance_category` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1062 DEFAULT CHARSET=utf8mb4 |

alter table exam add index(category_id);