-- 存量库：SKU / 订单申报增加「出口申报要素」DeclareElement
-- 可重复执行；仅在列不存在时 ADD。

SET @db := DATABASE();

-- c_sku.DeclareElement
SET @exists := (
  SELECT COUNT(1)
  FROM information_schema.COLUMNS
  WHERE TABLE_SCHEMA = @db
    AND TABLE_NAME = 'c_sku'
    AND COLUMN_NAME = 'DeclareElement'
);
SET @sql := IF(
  @exists = 0,
  'ALTER TABLE `c_sku` ADD COLUMN `DeclareElement` VARCHAR(255) NULL COMMENT ''出口申报要素'' AFTER `ImHsCode`',
  'SELECT ''c_sku.DeclareElement already exists'' AS info'
);
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

-- t_order_declaration.DeclareElement
SET @exists := (
  SELECT COUNT(1)
  FROM information_schema.COLUMNS
  WHERE TABLE_SCHEMA = @db
    AND TABLE_NAME = 't_order_declaration'
    AND COLUMN_NAME = 'DeclareElement'
);
SET @sql := IF(
  @exists = 0,
  'ALTER TABLE `t_order_declaration` ADD COLUMN `DeclareElement` VARCHAR(255) NULL COMMENT ''出口申报要素'' AFTER `ExHsCode`',
  'SELECT ''t_order_declaration.DeclareElement already exists'' AS info'
);
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;