XQuery中的全局变量，不确定如何返回平均值以及为什么会收到此错误

Question

I have been working on my 2nd simple query for a few days. All I am supposed to do is declare a global variable ($crimes) that points to all crime elements in the XML file and use a FLWOR query to iterate through each unique value of the day element so that I can see which days have the most crimes (it should be Saturday, Monday, and then Sunday in order). I also keep getting this error:

Unexpected end of query; variable "$crimes".

Code:

    xquery version "1.0";
delare variable $crimes := doc('dc_crime.xml')//crime;

(: 

   Query to display total number of crimes by
   day of the week
 :)
<results>{
    for $day in distinct-values(doc('dc_crime.xml')/$day
    let $crimes := sum($crimes/($day/$crimes))
    order by $day descending order

    return
    <crime day="{$day}" crimes="{$count}">{$crimes}</crime>
}</results>

Sample of XML:

       <crime id="13402531">
      <dateTime>2013-08-31T20:27:00</dateTime>
      <month>8-Aug</month>
      <day>7-Sat</day>
      <offense>THEFT/OTHER</offense>
      <method>OTHERS</method>
      <ward>3</ward>
   </crime>
   <crime id="13402533">
      <dateTime>2013-08-28T17:06:00</dateTime>
      <month>8-Aug</month>
      <day>4-Wed</day>
      <offense>THEFT F/AUTO</offense>
      <method>OTHERS</method>
      <ward>1</ward>
   </crime>
   <crime id="13402547">
      <dateTime>2013-08-31T20:05:00</dateTime>
      <month>8-Aug</month>
      <day>7-Sat</day>
      <offense>THEFT F/AUTO</offense>
      <method>OTHERS</method>
      <ward>6</ward>
   </crime>
   <crime id="13402704">
      <dateTime>2013-08-03T17:29:00</dateTime>
      <month>8-Aug</month>
      <day>7-Sat</day>
      <offense>THEFT/OTHER</offense>
      <method>OTHERS</method>
      <ward>2</ward>
   </crime>
</crimes>

Please help...

Answer 1

This is one possible XQuery that: 1. uses global variable and 2. count number of crimes per day and return the result in the order of that number, descending :

declare variable $crimes := doc('dc_crime.xml')//crime;

<results>{
    for $day in distinct-values(doc('dc_crime.xml')//day)
    (: get all crimes that happen at current day of week :)
    let $details := $crimes[day=$day] 
    (: count number crimes that happen at current day of week :)
    let $count := count($details)
    (: return the result in the order of $count, descending :)
    order by $count descending

    return
    <crime day="{$day}" crimes="{$count}">{$details}</crime>
}</results>

xpathtester demo

output :

<results>
   <crime crimes="3" day="7-Sat">
      <crime id="13402531"> 
         <dateTime>2013-08-31T20:27:00</dateTime>  
         <month>8-Aug</month>  
         <day>7-Sat</day>  
         <offense>THEFT/OTHER</offense>  
         <method>OTHERS</method>  
         <ward>3</ward> 
      </crime>
      <crime id="13402547"> 
         <dateTime>2013-08-31T20:05:00</dateTime>  
         <month>8-Aug</month>  
         <day>7-Sat</day>  
         <offense>THEFT F/AUTO</offense>  
         <method>OTHERS</method>  
         <ward>6</ward> 
      </crime>
      <crime id="13402704"> 
         <dateTime>2013-08-03T17:29:00</dateTime>  
         <month>8-Aug</month>  
         <day>7-Sat</day>  
         <offense>THEFT/OTHER</offense>  
         <method>OTHERS</method>  
         <ward>2</ward> 
      </crime>
   </crime>
   <crime crimes="1" day="4-Wed">
      <crime id="13402533"> 
         <dateTime>2013-08-28T17:06:00</dateTime>  
         <month>8-Aug</month>  
         <day>4-Wed</day>  
         <offense>THEFT F/AUTO</offense>  
         <method>OTHERS</method>  
         <ward>1</ward> 
      </crime>
   </crime>
</results>