在JOIN-ON/WHERE中无法识别子查询表别名

我想给一个业余朋友一些帮助,用SQL Server的经验来帮助MySQL。

SELECT ib.itemid, ii.realname as name, ib.stackSize,
       IFNULL(ah.price, '-') as price, ah.stock
    FROM item_basic ib
    LEFT OUTER JOIN item_info as ii ON ii.itemID = ib.itemID
    LEFT OUTER JOIN (SELECT price, COUNT(*) as stock
        FROM auction_house
        GROUP BY itemID) as AH on ii.itemID = AH.itemID -- erring line
    ORDER BY ii.realname

以及使用在FROM cluse而不是JOIN中组装子查询的版本,但这比这个版本麻烦得多。

这就产生了错误 Unknown column 'ah.itemID' in 'on clause'

如果我不正确地将错误行改为 ... ii.itemID = ib.itemID

这是一个 SQL Fiddle