SQL将多个列映射到同一个表

Question

我有数据，其中两列[Previous State]和[Next State]包含来自相同州列表的值。

我有一个单独的表，其中有两列将这些状态映射到更新的状态名称，如下所示：

State | Mapped State | --------+--------------+ 1 | a | 2 | b | 3 | b | 4 | c | 5 | d |

我想在查询中提取显示相对[Previous State]值的[Next State]和[Mapped State]。

当我两次加入状态映射表时，我抛出的代码错误：

SELECT a.[Name], b.[Mapped State] as [Previous State Mapped], c.[Mapped State] AS [Next State Mapped] 
FROM [Raw Data] a 
JOIN [Mapping Table] b ON a.[Previous State]=b.[State] 
JOIN [Mapping Table] c ON a.[Next State]=c.[State]

为什么这不起作用？感谢