Native queries provide a powerful way to execute complex queries without having to learn a new query language or resort to complicated object structures to model a predicate.
The query is somewhat complex but provides a realistic example of how someone can return multiple portions of XML data (for example, multiple XML nodes) and restrict results based on an XML predicate.
此查询比较复杂，但是更加真实；它演示如何返回 XML 数据的多个部分（例如多个 XML 节点）并根据 XML 谓词限制结果。
3
The XMLEXISTS predicate in the original query got converted into a complex expression that can be referred to using the number Q1.