-- 维护计划按批次归组：同一份周期计划共用 batch_id，列表按批次展示一级，展开看各期任务
ALTER TABLE `mes_device_prevent_task`
  ADD COLUMN `batch_id` varchar(64) DEFAULT NULL COMMENT '计划批次' AFTER `prevent_id`;

UPDATE `mes_device_prevent_task` t
JOIN (
  SELECT MIN(id) AS batch_id, prevent_id, device_id, IFNULL(user_code, '') AS user_code, create_date
  FROM `mes_device_prevent_task`
  GROUP BY prevent_id, device_id, IFNULL(user_code, ''), create_date
) g ON t.prevent_id <=> g.prevent_id
   AND t.device_id <=> g.device_id
   AND IFNULL(t.user_code, '') = g.user_code
   AND t.create_date <=> g.create_date
SET t.batch_id = g.batch_id
WHERE t.batch_id IS NULL OR t.batch_id = '';

UPDATE `mes_device_prevent_task`
SET `batch_id` = `id`
WHERE `batch_id` IS NULL OR `batch_id` = '';

ALTER TABLE `mes_device_prevent_task`
  ADD INDEX `idx_prevent_task_batch_id` (`batch_id`);