多部分标识符无法绑定但没有连接问题？

Question

我在MS Server Management studio v11.02上运行以下内容 但是'我收到的错误是：

The multi-part identifier "PO.LastPo" could not be bound.

我有什么想法可以解决这个问题？

SELECT DISTINCT PO.LastPo
    INTO #IncludedPoll
    FROM
    (
            -- Inner query makes sure member was actually enrolled for 2 yrs
            SELECT LastPo, COUNT(*) AS Periods
            FROM [Cye].[2_output_lastPoll] PO
            WHERE PO.PollPq IN (1,2)
            GROUP BY LastPo
    ) A
    WHERE Periods IN (1,2) AND A.LastPo NOT IN (SELECT LastPo FROM #FilterPoll)

#FilterPoll是一个临时表，我很好，并且包含一些我想要从#IncludedPoll临时表中过滤掉的ID。

我已经看过其他答案，但它们都与连接相关，这不应该是一个问题。

Answer 1

您将内部查询命名为A，因此它应为SELECT DISTINCT A.LastPo而不是PO.LastPo