Question

为什么没有编译此更新语句？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))

Answer 1

我认为您需要在UPDATE中引用自我JOIN的Alias。至少我刚尝试了一个带有自我JOIN的UPDATE，并且以下类型的语法对我有效。

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))

表'dbo.UserProperties'不明确。为什么会出现这个错误？

1 个答案: