-- MySQL 8.0.16+；对Lastleg连接的实例完整执行，遇错停止。DDL隐式提交。
USE `baiyue_lastleg`;
SET NAMES utf8mb4;
SELECT DATABASE() AS target_database, @@hostname AS mysql_host, @@port AS mysql_port;

-- 整箱废弃后保留SKU明细，剩余数量允许归零，仍禁止负库存。
-- 原子替换约束，可重复执行；不修改业务记录。
SET @ddl = IF(EXISTS (
  SELECT 1 FROM information_schema.table_constraints
  WHERE constraint_schema=DATABASE() AND table_name='ll_return_inventory_carton_item'
    AND constraint_name='chk_ll_return_inventory_carton_item_quantity'
),
  'ALTER TABLE ll_return_inventory_carton_item DROP CHECK chk_ll_return_inventory_carton_item_quantity, ADD CONSTRAINT chk_ll_return_inventory_carton_item_quantity CHECK(quantity>=0)',
  'ALTER TABLE ll_return_inventory_carton_item ADD CONSTRAINT chk_ll_return_inventory_carton_item_quantity CHECK(quantity>=0)'
);
PREPARE stmt FROM @ddl;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

SHOW CREATE TABLE ll_return_inventory_carton_item;