-- 框架合同调价函支持多张图片：OSS ID 列表 JSON 存储
ALTER TABLE `crm_contract_product_price_tier`
  ADD COLUMN `letter_oss_ids` VARCHAR(4000) NULL COMMENT '调价函OSS ID列表(JSON字符串数组，如["id1","id2"])' AFTER `price`;

-- 历史单附件迁移为单元素 JSON 数组
UPDATE `crm_contract_product_price_tier`
SET `letter_oss_ids` = CONCAT('["', CAST(`letter_oss_id` AS CHAR), '"]')
WHERE `letter_oss_id` IS NOT NULL AND (`letter_oss_ids` IS NULL OR `letter_oss_ids` = '');

ALTER TABLE `crm_contract_product_price_tier`
  MODIFY COLUMN `letter_oss_id` BIGINT(20) NULL COMMENT '调价函单附件OSS ID(废弃，请使用 letter_oss_ids)';