Get element with min attribute

问题

With Xquery I want to get the row which has the min sortOrder. In the example below the row with id=3.

<table>
  <row id="1"><attribute identifier="sortOrder">120</attribute><attribute identifier="mainContent">Test 3</attribute></row>
  <row id="2"><attribute identifier="sortOrder">130</attribute><attribute identifier="mainContent">Test 1</attribute></row>
  <row id="3"><attribute identifier="sortOrder">10</attribute><attribute identifier="mainContent">Test 2</attribute></row>
</table>

Anyone got a hint?

回答1:

find min value with the min() function and then look it up in the rows:

let $min := min(//row/attribute[@identifier='sortOrder'])
return //row[attribute[@identifier='sortOrder'] = $min]

回答2:

If you have access to an XQuery 3.0 implementation, then I am quite taken by this functional approach:

xquery version "3.0";

let $apply := function($xs, $f, $xpath) {
  $xpath($xs[. = $f($xs)])
} return


$apply(
    //row/attribute[@identifier eq 'sortOrder'],
    fn:min#1,
    function($x) {
        $x/parent::node()
    }
)

One of the nice properties of this approach is you only need to do the search on the initial data once i.e. //row/attribute[@identifier eq 'sortOrder'] only needs to be evaluated once, which may be more efficient.

Another nice property is that the lambda $apply is a generic function, and so you could re-use it for any function that would operate on $xs for example fn:max#1 :-)

来源：https://stackoverflow.com/questions/25641740/get-element-with-min-attribute

标签

xml

xquery