-- 小程序 VIN 车辆绑定字段（app_user_id）
-- 说明：绑定列统一命名为 app_user_id，脚本幂等可重复执行

SET @column_exists := (
  SELECT COUNT(1)
  FROM information_schema.COLUMNS
  WHERE TABLE_SCHEMA = DATABASE()
    AND TABLE_NAME = 't_vin_management'
    AND COLUMN_NAME = 'app_user_id'
);
SET @column_sql := IF(
  @column_exists = 0,
  'ALTER TABLE `t_vin_management` ADD COLUMN `app_user_id` BIGINT NULL COMMENT ''绑定的小程序用户ID'' AFTER `del_flag`',
  'SELECT 1'
);
PREPARE column_stmt FROM @column_sql;
EXECUTE column_stmt;
DEALLOCATE PREPARE column_stmt;

SET @index_exists := (
  SELECT COUNT(1)
  FROM information_schema.STATISTICS
  WHERE TABLE_SCHEMA = DATABASE()
    AND TABLE_NAME = 't_vin_management'
    AND INDEX_NAME = 'idx_app_user_id'
);
SET @index_sql := IF(
  @index_exists = 0,
  'ALTER TABLE `t_vin_management` ADD INDEX `idx_app_user_id` (`app_user_id`)',
  'SELECT 1'
);
PREPARE index_stmt FROM @index_sql;
EXECUTE index_stmt;
DEALLOCATE PREPARE index_stmt;