-- Create task_completions table to track which user completed which task
CREATE TABLE IF NOT EXISTS `task_completions` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `user_id` int(11) NOT NULL,
  `task_id` int(11) NOT NULL,
  `completed_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`),
  UNIQUE KEY `user_task` (`user_id`, `task_id`),
  KEY `user_id` (`user_id`),
  KEY `task_id` (`task_id`),
  FOREIGN KEY (`user_id`) REFERENCES `users` (`id`),
  FOREIGN KEY (`task_id`) REFERENCES `tasks` (`id`) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;