这些查询通常需要子文档级访问来运算谓词和提取文档片段。

These queries always require sub-document level access to evaluate predicates and to extract document fragments.

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DB 2使用XSCAN操作符来遍历XML文档树，如需要，还将计算谓词和提取文档片断和值。

DB2 USES the XSCAN operator to traverse XML document trees and, if needed, to evaluate predicates and extract document fragments and values.

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Query Q5 对谓词使用索引表，但是需要提取函数（具有 XML 分析）来检索客户电子邮件地址。

Query Q5 uses side tables for the predicates, but requires an extract function (with XML parsing) to retrieve the customers email addresses.

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