如何使用 Xquery 从两个 XML 文件中获取数据？答案

【问题标题】：How to get data from two XML file using Xquery?如何使用 Xquery 从两个 XML 文件中获取数据？
【发布时间】：2012-08-21 13:58:31
【问题描述】：

Sample1.xml

<data><row><id>949459</id><product_id>4119945117</product_id></row>
    <row><id>781351</id><product_id>1009460692</product_id></row>
    <row><id>780163</id><product_id>1009755673</product_id></row>
    <row><id>1017226</id><product_id>1013393868</product_id></row>
    <row><id>1017956</id><product_id>1013393871</product_id></row>
    <row><id>1017310</id><product_id>1013393874</product_id></row>
    <row><id>771708</id><product_id>4388803569</product_id></row>
    <row><id>3270790</id><product_id>1013679270</product_id></row>
    <row><id>775869</id><product_id>1014142699</product_id></row>
    <row><id>1017599</id><product_id>1021870484</product_id></row>
    <row><id>1018789</id><product_id>1021870489</product_id></row>
    <row><id>1017091</id><product_id>1021870491</product_id></row>
    <row><id>1017333</id><product_id>1021870492</product_id></row>
    <row><id>1017630</id><product_id>1021870493</product_id></row>
    <row><id>1017774</id><product_id>1021870495</product_id></row>
    <row><id>1018192</id><product_id>1021870496</product_id></row>
    <row><id>1018725</id><product_id>4408034849</product_id></row>
    <row><id>1017990</id><product_id>1021870498</product_id></row>
    <row><id>1018027</id><product_id>1021870499</product_id></row>
    <row><id>1017166</id><product_id>1021870500</product_id></row>
    <row><id>769120</id><product_id>1032140806</product_id></row>
    <row><id>950336</id><product_id>1035310069</product_id></row>
    </data>

sample2.xml

<productSet>
 <row><product>4388803569</product></row>
 <row><product>4408034289</product></row>
 <row><product>4408034589</product></row>
 <row><product>4408034849</product></row>
 <row><product>4094557957</product></row>
 <row><product>4119945117</product></row>
</productSet>

这是我的 Xquery，通过与示例 2 文件中的 product_id 元素进行比较，返回来自 sample1 XML 文件的所有产品元素值。在这里，我试图检索所有不可用的产品。

<outProduct_10310>
{ for $b in doc("sample1.xml")/data/row,
      $a in doc("sample2.xml")/productSet/row[product != $b/product_id]
  return   
      <op_id> { $b/product_id/text() } </op_id>
  }  </outProduct_10310>

当我用等号比较这两个 XML 但我想检索不匹配的数据时，此代码将返回正确的匹配数据，但如果我运行上面的代码，它会给出以下输出：

<outProduct_10310>
  <op_id>4119945117</op_id>
  <op_id>4119945117</op_id>
  <op_id>4119945117</op_id>
  <op_id>4119945117</op_id>
  <op_id>4119945117</op_id>
  <op_id>1009460692</op_id>
  <op_id>1009460692</op_id>
  <op_id>1009460692</op_id>
  <op_id>1009460692</op_id>
  <op_id>1009460692</op_id>
  <op_id>1009460692</op_id>
  <op_id>1009755673</op_id>
  <op_id>1009755673</op_id>
  <op_id>1009755673</op_id>
  <op_id>1009755673</op_id>
  <op_id>1009755673</op_id>
  <op_id>1009755673</op_id>
  <op_id>1013393868</op_id>
  <op_id>1013393868</op_id>
  <op_id>1013393868</op_id>
  <op_id>1013393868</op_id>
  <op_id>1013393868</op_id>
  <op_id>1013393868</op_id>
  <op_id>1013393871</op_id>
  <op_id>1013393871</op_id>
  <op_id>1013393871</op_id>
  <op_id>1013393871</op_id>
  <op_id>1013393871</op_id>
  <op_id>1013393871</op_id>
  <op_id>1013393874</op_id>
  <op_id>1013393874</op_id>
  <op_id>1013393874</op_id>
  <op_id>1013393874</op_id>
  <op_id>1013393874</op_id>
  <op_id>1013393874</op_id>
  <op_id>4388803569</op_id>
  <op_id>4388803569</op_id>
  <op_id>4388803569</op_id>
  <op_id>4388803569</op_id>
  <op_id>4388803569</op_id>
  <op_id>1013679270</op_id>
  <op_id>1013679270</op_id>
  <op_id>1013679270</op_id>
  <op_id>1013679270</op_id>
  <op_id>1013679270</op_id>
  <op_id>1013679270</op_id>
  <op_id>1014142699</op_id>
  <op_id>1014142699</op_id>
  <op_id>1014142699</op_id>
  <op_id>1014142699</op_id>
  <op_id>1014142699</op_id>
  <op_id>1014142699</op_id>
  <op_id>1021870484</op_id>
  <op_id>1021870484</op_id>
  <op_id>1021870484</op_id>
  <op_id>1021870484</op_id>
  <op_id>1021870484</op_id>
  <op_id>1021870484</op_id>
  <op_id>1021870489</op_id>
  <op_id>1021870489</op_id>
  <op_id>1021870489</op_id>
  <op_id>1021870489</op_id>
  <op_id>1021870489</op_id>
  <op_id>1021870489</op_id>
  <op_id>1021870491</op_id>
  <op_id>1021870491</op_id>
  <op_id>1021870491</op_id>
  <op_id>1021870491</op_id>
  <op_id>1021870491</op_id>
  <op_id>1021870491</op_id>
  <op_id>1021870492</op_id>
  <op_id>1021870492</op_id>
  <op_id>1021870492</op_id>
  <op_id>1021870492</op_id>
  <op_id>1021870492</op_id>
  <op_id>1021870492</op_id>
  <op_id>1021870493</op_id>
  <op_id>1021870493</op_id>
  <op_id>1021870493</op_id>
  <op_id>1021870493</op_id>
  <op_id>1021870493</op_id>
  <op_id>1021870493</op_id>
  <op_id>1021870495</op_id>
  <op_id>1021870495</op_id>
  <op_id>1021870495</op_id>
  <op_id>1021870495</op_id>
  <op_id>1021870495</op_id>
  <op_id>1021870495</op_id>
  <op_id>1021870496</op_id>
  <op_id>1021870496</op_id>
  <op_id>1021870496</op_id>
  <op_id>1021870496</op_id>
  <op_id>1021870496</op_id>
  <op_id>1021870496</op_id>
  <op_id>4408034849</op_id>
  <op_id>4408034849</op_id>
  <op_id>4408034849</op_id>
  <op_id>4408034849</op_id>
  <op_id>4408034849</op_id>
  <op_id>1021870498</op_id>
  <op_id>1021870498</op_id>
  <op_id>1021870498</op_id>
  <op_id>1021870498</op_id>
  <op_id>1021870498</op_id>
  <op_id>1021870498</op_id>
  <op_id>1021870499</op_id>
  <op_id>1021870499</op_id>
  <op_id>1021870499</op_id>
  <op_id>1021870499</op_id>
  <op_id>1021870499</op_id>
  <op_id>1021870499</op_id>
  <op_id>1021870500</op_id>
  <op_id>1021870500</op_id>
  <op_id>1021870500</op_id>
  <op_id>1021870500</op_id>
  <op_id>1021870500</op_id>
  <op_id>1021870500</op_id>
  <op_id>1032140806</op_id>
  <op_id>1032140806</op_id>
  <op_id>1032140806</op_id>
  <op_id>1032140806</op_id>
  <op_id>1032140806</op_id>
  <op_id>1032140806</op_id>
  <op_id>1035310069</op_id>
  <op_id>1035310069</op_id>
  <op_id>1035310069</op_id>
  <op_id>1035310069</op_id>
  <op_id>1035310069</op_id>
  <op_id>1035310069</op_id>
</outProduct_10310>

我对 xquery 完全陌生。谁能帮助我如何只获取不匹配的数据？

【问题讨论】：

标签： xquery basex

【解决方案1】：

首先，您不需要使用 for 循环比较所有 id 对，因为如果您提供序列，标准 = 运算符将搜索相等的值。

因此，查找所有匹配产品的更简单方法是：

<outProduct_10310>
{ for $b in doc("sample1.xml")/data/row[product_id = doc("sample2.xml")/productSet/row/product]
  return   
      <op_id> { $b/product_id/text() } </op_id>
  }  
</outProduct_10310>

对于不匹配的产品，您可以只选择所有与 not 运算符不匹配的产品：（请注意，您不能在此处使用 !=，因为总会有不同的 id）

<outProduct_10310>
{ for $b in doc("sample1.xml")/data/row[not (product_id = doc("sample2.xml")/productSet/row/product) ]
  return   
      <op_id> { $b/product_id/text() } </op_id>
  }  
</outProduct_10310>

根据您的 XQuery 引擎有多好，您可能希望将 doc("sample2.xml")/productSet/row 移出 [..] 括号并将其存储在变量中。

【讨论】：

是的，它奏效了。你指明了方向。我必须了解更多关于 xquery 的信息。感谢回复

【解决方案2】：

请注意，所有一般比较（=、!=、...）都会将左操作数的所有项与右操作数的所有项目。一旦比较成功（即产生true），结果也将为真。例如，(1,2) != (1,2) 将返回 true，因为单个比较 1 != 2 会产生 true。

在您的特定查询中，您可以尝试 not(product = $b/product_id)，它只会在没有单一比较产生 true 的情况下返回 true。

【讨论】：

感谢您的回复。我在查询中尝试了 not(product = $b/product_id) 但它返回相同的输出。我无法获得准确的不匹配数据