ALTER TABLE `person`
  ADD COLUMN `main_department_id` INT NULL;

CREATE INDEX `person_main_department_id_idx`
  ON `person`(`main_department_id`);

ALTER TABLE `person`
  ADD CONSTRAINT `person_main_department_id_fkey`
  FOREIGN KEY (`main_department_id`) REFERENCES `department`(`id`)
  ON DELETE SET NULL
  ON UPDATE CASCADE;

CREATE TABLE `person_department` (
  `person_id` INT NOT NULL,
  `department_id` INT NOT NULL,
  `created_at` DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
  `updated_at` DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),

  PRIMARY KEY (`person_id`, `department_id`),
  INDEX `person_department_department_id_idx`(`department_id`),
  CONSTRAINT `person_department_person_id_fkey`
    FOREIGN KEY (`person_id`) REFERENCES `person`(`id`)
    ON DELETE CASCADE
    ON UPDATE CASCADE,
  CONSTRAINT `person_department_department_id_fkey`
    FOREIGN KEY (`department_id`) REFERENCES `department`(`id`)
    ON DELETE CASCADE
    ON UPDATE CASCADE
) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

UPDATE `person` AS `p`
LEFT JOIN `department` AS `d`
  ON `d`.`source_group_id` = `p`.`source_main_department_id`
SET `p`.`main_department_id` = `d`.`id`
WHERE `p`.`source_system` = 'ding_hr'
  AND `p`.`source_main_department_id` IS NOT NULL;

INSERT INTO `person_department` (`person_id`, `department_id`, `created_at`, `updated_at`)
SELECT DISTINCT
  `id`,
  `main_department_id`,
  CURRENT_TIMESTAMP(3),
  CURRENT_TIMESTAMP(3)
FROM `person`
WHERE `main_department_id` IS NOT NULL
ON DUPLICATE KEY UPDATE
  `updated_at` = VALUES(`updated_at`);