Question

<?xml version="1.0" encoding="UTF-8"?>
<library>
    <books>
        <book>
            <title>The Story of my Life </title>
            <accessionNumber val="1"/>
        </book>
        <book>
            <title>XML Schema </title>
            <accessionNumber val="2"/>
        </book>
        <book>
            <title>C++ for Image processing</title>
            <accessionNumber val="3"/>
        </book>
    </books>
    <loans>
        <loan book="1" user="35" dueDate="25-April-2010"/>
    </loans>
    <loans>
        <loan book="3" user="400" dueDate="05-Jan-2010"/>
    </loans>
    <loans>
        <loan book="2" user="02" dueDate="25-Feb-2010"/>
    </loans>
    <users>
        <user>
            <name>Fred Jame</name>
            <id val="35"/>
        </user>
        <user>
            <name>Ashley</name>
            <id val="400"/>
        </user>
        <user>
            <name>Patrick</name>
            <id val="02"/>
        </user>
    </users>
</library>

我的任务是编写XQuery Expression，列出贷款逾期的所有用户。

我必须使用fn:current-date()函数与dueDate进行比较才能找出所有逾期用户，但此处的问题是fn:current-date()格式，而且XML文档中的dueDate格式完全不同

如何格式化以获得我想要的结果？

for $x in doc("library.xml")/library
where  $x/@dueDate > fn:current-date()
return $x/@name

我在上面尝试过但fn:current-date()将日期输出设为2014-03-30Z

但如果dueDate高于Current-Date，我需要将dueDate与当前日期进行比较，然后显示所有用户。

Answer 1

由于这显然是一项练习，我不会提供完整的答案，而是草拟解决方案。

很难比较XML文档中使用的日期格式。创建一个执行以下步骤的函数可能是合理的（但当然也可以在没有一个的情况下完成）：
- 您必须tokenize(...)，将月份解析为数字并将其连接为YYYY-mm-dd
- 现在，您可以使用xs:date($string)将其转换为日期对象。
现在循环遍历所有<loan/>元素，并在where子句中过滤它们以获取到期贷款，调用您编写的函数或将代码放在此处。
最后一步，您必须将<loan/>个对象解析为相应的用户。

这应该可以帮助您编写代码。如果您有任何进一步的具体问题或遇到问题，请随时发布后续问题（与您尝试过的一样）！

更新：这是我的代码，使用index-of查找月份。 resolveDate函数在代码中被注释，剩下的查询很简单。

declare function local:resolveDate($date as xs:string) as xs:date {
  (: Month index, so we can look it up :)
  let $months := ("Jan", "Feb", "March", "April", "May", "June", "July", "Aug", "Sep", "Oct", "Nov", "Dec")
  (: Split up the date :)
  let $date := tokenize($date, '-')
  (: Resolve the month to its two digit number :)
  let $month := index-of($months, $date[2]) cast as xs:string
  let $month := if (string-length($month) < 2)
                then concat('0', $month)
                else $month
  (: Construct an xs:date object from the reordered date :)
  let $date := string-join(($date[3], $month , $date[1]), '-')
  return xs:date($date)
};

for $user in //user
for $loan in //loan[@user=$user/id/@val]
where local:resolveDate($loan/@dueDate) < current-date()
return $user

Answer 2

您可以创建如下函数：

declare function local:xml_month

($monthId as xs:string) as xs:string
{
if (tokenize($monthId,"-")[2] = 'January')
then  
concat(  tokenize($monthId,"-")[1],"-",
replace(tokenize($monthId,"-")[2],'January','01'),"-",
tokenize($monthId,"-")[3])
else if (tokenize($monthId,"-")[2] = 'February')
then  
concat(  tokenize($monthId,"-")[1],"-",
replace(tokenize($monthId,"-")[2],'February','02'),"-",
tokenize($monthId,"-")[3])
else if (tokenize($monthId,"-")[2] = 'March')
then  
concat(  tokenize($monthId,"-")[1],"-",
replace(tokenize($monthId,"-")[2],'March','03'),"-",
tokenize($monthId,"-")[3])
else if (tokenize($monthId,"-")[2] = 'April')
then  
concat(  tokenize($monthId,"-")[1],"-",
replace(tokenize($monthId,"-")[2],'April','04'),"-",
tokenize($monthId,"-")[3])
else if (tokenize($monthId,"-")[2] = 'May')
then  
concat(  tokenize($monthId,"-")[1],"-",
replace(tokenize($monthId,"-")[2],'May','05'),"-",
tokenize($monthId,"-")[3])
else if (tokenize($monthId,"-")[2] = 'June')
then  
concat(  tokenize($monthId,"-")[1],"-",
replace(tokenize($monthId,"-")[2],'June','06'),"-",
tokenize($monthId,"-")[3])
else if (tokenize($monthId,"-")[2] = 'July')
then  
concat(  tokenize($monthId,"-")[1],"-",
replace(tokenize($monthId,"-")[2],'July','07'),"-",
tokenize($monthId,"-")[3])
else if (tokenize($monthId,"-")[2] = 'August')
then  
concat(  tokenize($monthId,"-")[1],"-",
replace(tokenize($monthId,"-")[2],'August','08'),"-",
tokenize($monthId,"-")[3])
else if (tokenize($monthId,"-")[2] = 'September')
then  
concat(  tokenize($monthId,"-")[1],"-",
replace(tokenize($monthId,"-")[2],'Sempter','09'),"-",
tokenize($monthId,"-")[3])
else if (tokenize($monthId,"-")[2] = 'October')
then  
concat(  tokenize($monthId,"-")[1],"-",
replace(tokenize($monthId,"-")[2],'October','10'),"-",
tokenize($monthId,"-")[3])
else if (tokenize($monthId,"-")[2] = 'November')
then  
concat(  tokenize($monthId,"-")[1],"-",
replace(tokenize($monthId,"-")[2],'November','11'),"-",
tokenize($monthId,"-")[3])
else if (tokenize($monthId,"-")[2] = 'December')
then  
concat(  tokenize($monthId,"-")[1],"-",
replace(tokenize($monthId,"-")[2],'December','12'),"-",
tokenize($monthId,"-")[3])    
else "NA"
};

for $u in doc("ques2010.xml")//user
for $l in doc("ques2010.xml")//loan    
where fn:current-date() > xs:date(local:xml_month($l/data(@dueDate)))
and $u/id/@val = $l/@user
return $u/name

它应该适合你。

xquery fn：current-date（）格式

2 个答案: