列出DBpedia的国家 [英] List countries from DBpedia

问题描述

尝试查询DBpedia以获取具有 dbo：longName 属性和列出的每个国家的首都的所有国家/地区的列表，但返回0个结果。无法看到查询出了什么问题。

Trying to query DBpedia for a list of all countries with the dbo:longName property and the capital of each country listed but get 0 results returned. Can't see whats wrong with the query.

PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX dbr: <http://dbpedia.org/resource/>

SELECT ?country ?capital
WHERE {
 ?country a dbo:longName ;
    dbo:capital ?capital .
}

缺少什么？

推荐答案

您丢失了？country 的 rdf：type 的信息 dbo：Country 而不是 dbo：longName 。正确的查询应该是：

You are missing that ?country has a rdf:type of dbo:Country and not dbo:longName. The right query should be:

PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX dbr: <http://dbpedia.org/resource/>

SELECT ?country ?capital
WHERE {
 ?x a dbo:Country.
 ?x dbo:longName ?country.
 ?x dbp:capital ?capital
}

---

更新

根据您的评论，您需要国家的URI及其首都。因此，您不需要 dbo：longName ，因为您不需要国家标签名称。您将选择实例：

---

Update

Based on your comment you want the URI's of the country and their capital. Therefore, you don't need dbo:longName, because you don't want the country label name. You will select the instances:

PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX dbr: <http://dbpedia.org/resource/>

SELECT ?country ?capital
WHERE {
 ?country a dbo:Country.
 ?country dbo:capital ?capital
}

请注意，结果将使已经灭绝的国家。如果要过滤已结束的国家/地区，则应使用以下命令获得此结果：

Note that results will bring countries that are extinct. If you want to filter countries that have ended, you should get this result with:

PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX dbr: <http://dbpedia.org/resource/>

SELECT ?country ?capital
WHERE {
 ?country a dbo:Country.
 ?country dbo:capital ?capital.
 FILTER NOT EXISTS { ?country dbo:dissolutionYear ?yearEnd }
}

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