对于选择元素集合中的第一个元素，最容易的方法是利用值 1 的谓词。
The easiest method for selecting the first in a set of elements is with a predicate of value 1.
仅当第一个谓词认为行不合格时第二个谓词才应用。
The second predicate is applied only when the row is disqualified by the first predicate.
在第一个查询中，过滤谓词是在由xmltable函数生成的char列“Zip”上表达的。
In the first query, the filtering predicate is expressed on the CHAR column "Zip" generated by the XMLTABLE function.
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