Sql 表格'；dbo.UserProperties'；这是模棱两可的。为什么会出现这种错误？

为什么未编译此update语句？根据msdn，这是完全正确的

UPDATE  dbo.UserProperties
  SET     Value = MergeFrom.Value
FROM    dbo.UserProperties MergeFrom ,
        dbo.UserProperties MergeTo
WHERE   MergeFrom.Field = MergeTo.Field
        AND MergeTo.[Key] = CAST(@MergeToUserID AS NVARCHAR(50))
        AND MergeFrom.[Key] = CAST(@MergeFromUserID AS NVARCHAR(50))

---

我认为您需要在更新中引用别名以进行自连接。至少我刚刚尝试了一个带有自连接的更新，下面的语法对我很有用

UPDATE  MergeTo
    SET MergeTo.Value = MergeFrom.Value
FROM dbo.UserProperties AS MergeFrom INNER JOIN
          dbo.UserProperties AS MergeTo ON MergeFrom.Field = MergeTo.Field
WHERE   MergeTo.[Key] = CAST(@MergeToUserID AS NVARCHAR(50))
                        AND MergeFrom.[Key] = CAST(@MergeFromUserID AS NVARCHAR(50))