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<td width="90%"><font size="4" face="Verdana, Arial, Helvetica"><b>包含對象的查詢</b></font></td><td width="200" align="right"><font size="1" face="Verdana, Arial, Helvetica"><nobr>   第 7 頁（共11 頁）</nobr></font></td>
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<p>最后一個查詢示例稱為<i>包含（containment）</i>查詢。基本上，我們要搜索所有部門以查找特定雇員（而不是象上一個查詢，搜索單一部門查找特定雇員）。
</p>
<p>要構建包含查詢，我們使用第二個查詢概念（第一個是參數），它就是所謂的<i>查詢變量</i>。變量有助于限制查詢的結果。在以下示例中，變量用于指定姓與選中的查詢參數相同的所有 <code>PersonImpl</code>。基本上，變量允許我們進一步限制部門中的雇員集合。</p>
<pre>
<code style="font-family: Courier New, Courier, monospace; font-size: 12">
Extent deptExtent = pm.getExtent(DepartmentImpl.class, false);
String personVar =
         "com.stereobeacon.jdo.tutorial.PersonImpl person";
String containFilter =
         "employees.contains(person) &amp; person.lastName==name";
String nameParam = "String name";
Query personQuery = pm.newQuery(deptExtent, containFilter);
q.declareParameters(nameParam);
q.declareVariables(personVar);

Collection personColl =
         (Collection) personQuery.execute("Williams");
</code>
</pre>
<p>請注意，本質上，聲明變量的方法與參數相同。變量與傳遞給查詢執行子句的參數無關，因為變量是在過濾器內使用的元素，而不是用于過濾器信息的參數設置。</p>
<p>最后，請注意該查詢和多對象查詢在 LiDO 版本 1.0 下<i>不</i>能工作。LIBeLIS 團隊意識到了這個錯誤，并正努力解決它。</p>
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