-- 已有库增量：包裹明细增加商品图片 ImageUrl
-- 可重复执行

SET @col_exists := (
  SELECT COUNT(1)
  FROM information_schema.COLUMNS
  WHERE TABLE_SCHEMA = DATABASE()
    AND TABLE_NAME = 'C_parcel_item'
    AND COLUMN_NAME = 'ImageUrl'
);

SET @sql := IF(
  @col_exists = 0,
  'ALTER TABLE `C_parcel_item` ADD COLUMN `ImageUrl` VARCHAR(1024) NULL COMMENT ''商品图片URL'' AFTER `AttributeText`',
  'SELECT ''C_parcel_item.ImageUrl already exists'' AS info'
);

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;