SQL Server：将表达式转换为数据类型 bigint 时出现算术溢出错误

这是我的查询顺序：

SELECT
      CASE
         WHEN ((BarCode IS NOT NULL) AND (ExternelBarCode IS NULL)) THEN BarCode
         WHEN ((BarCode IS NULL) AND (ExternelBarCode IS NOT NULL)) THEN CAST(ExternelBarCode AS bigint)
         ELSE ExternelBarCode -- When both exist
      END AS TicketBarCode
...

当我运行它时，我收到以下消息：

将表达式转换为数据类型 bigint 时出现算术溢出错误。

专栏BarCode属于类型bigint，和列ExternelBarCode属于类型varchar(250).

BarCode = 178625624324,
ExternelBarCode = 2015591149641227565492

我该如何解决这个问题？

值 2,015,591,149,641,227,565,492 大于允许的最大值bigint2^63-1 (9,223,372,036,854,775,807) 因此无法进行转换。

如果需要返回数值，可以将其转换为decimal(38,0)

SELECT
      CASE
         WHEN ((BarCode IS NOT NULL) AND (ExternelBarCode IS NULL)) THEN CAST(BarCode as decimal(38,0))
         WHEN ((BarCode IS NULL) AND (ExternelBarCode IS NOT NULL)) THEN CAST(ExternelBarCode AS decimal(38,0))
         ELSE cast(ExternelBarCode as decimal(38,0)) -- When both exist
      END AS TicketBarCode