-- 手工派车日历增加可空数量文本。单位固定为吨，最多两位小数，不参与车次汇总。
-- MySQL 5.7 / utf8mb4。可重复执行。
SET NAMES utf8mb4;

SET @col_exists = (
  SELECT COUNT(*) FROM information_schema.COLUMNS
  WHERE TABLE_SCHEMA = DATABASE()
    AND TABLE_NAME = 'pl_dispatch_calendar'
    AND COLUMN_NAME = 'quantity'
);
SET @ddl = IF(
  @col_exists = 0,
  'ALTER TABLE `pl_dispatch_calendar` ADD COLUMN `quantity` varchar(16) DEFAULT NULL COMMENT ''数量文本（吨），最多两位小数，不参与汇总'' AFTER `destination`',
  'SELECT 1'
);
PREPARE stmt FROM @ddl;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;