FOR XML EXPLICIT 查询中的每个 IDREFS 或 NMTOKENS 列必须出现在单独的 SELECT 子句中，并且这些实例都必须直接排列在它们所属的元素之后。

Every IDREFS or NMTOKENS column in a FOR XML EXPLICIT query must appear in a separate SELECT clause, and the instances must be ordered directly after the element to which they belong.