-- 重量段增加体积上限。长x宽x高记在这一档上，不记成费用。可重复执行。
SET NAMES utf8mb4;

SET @ddl = (
  SELECT IF(
    EXISTS (
      SELECT 1 FROM information_schema.COLUMNS
      WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = 'pay_weight_band' AND COLUMN_NAME = 'volume_text'
    ),
    'SELECT 1',
    'ALTER TABLE pay_weight_band ADD COLUMN volume_text varchar(40) DEFAULT NULL COMMENT ''体积上限，数字加单位，如10000cm³'' AFTER weight_max'
  )
);
PREPARE stmt FROM @ddl;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;