2

からの選択順序を制御するにはどうすればよいfor $x in (...)ですか? $retmax以下の XQuery の最後の行では、結果を , の順序にしたいのですが$retmin、逆の順序で出力されます。

<result>
{
    let $max := max(doc("countries.xml")//country/(@population div @area))
    let $min := min(doc("countries.xml")//country/(@population div @area))
    for $country in doc("countries.xml")//country
    let $density := $country/(@population div @area)
    let $ret_min := if ($density = $min)
                    then <lowest density="{$density}">{data($country/@name)}</lowest>
                    else ()
    let $ret_max := if ($density = $max) 
                    then <highest density="{$density}">{data($country/@name)}</highest>
                    else ()
    for $r in ($ret_max, $ret_min) return $r
}   
</result>

生成:

  <result>
    <lowest density="0.026752619966905682">Greenland</lowest>
    <highest density="31052.3125">Macau</highest>
  </result>

でも私はしたい：

  <result>
    <highest density="31052.3125">Macau</highest>
    <lowest density="0.026752619966905682">Greenland</lowest>
  </result>
4

1 に答える 1

1

こう書くと・・・

let $ordered_countries := for $country in doc("countries.xml")//country
                          let $density := $country/(@population div @area)
                          order by $density 
                          return $country
let $low  := $ordered_countries[1]
let $high := $ordered_countries[fn:last()]
return (
    <lowest density="{$low/(@population div @area)}">{data($low/@name)}</lowest>,
    <highest density="{$high/(@population div @area)}">{data($high/@name)}</highest>
)
于 2012-07-29T09:00:08.927 に答える