CREATE TABLE IF NOT EXISTS topics (
  id BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
  parent_id BIGINT UNSIGNED NULL,
  name VARCHAR(191) NOT NULL,
  sort_order INT NOT NULL DEFAULT 1000,
  created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
  updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  CONSTRAINT fk_topics_parent FOREIGN KEY (parent_id) REFERENCES topics(id) ON DELETE CASCADE,
  KEY idx_topics_parent_sort (parent_id, sort_order, id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

CREATE TABLE IF NOT EXISTS photo_topics (
  photo_id BIGINT UNSIGNED NOT NULL,
  topic_id BIGINT UNSIGNED NOT NULL,
  created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (photo_id, topic_id),
  CONSTRAINT fk_photo_topics_photo FOREIGN KEY (photo_id) REFERENCES photos(id) ON DELETE CASCADE,
  CONSTRAINT fk_photo_topics_topic FOREIGN KEY (topic_id) REFERENCES topics(id) ON DELETE CASCADE,
  KEY idx_photo_topics_topic (topic_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;