我遵循了 SPARQL 1.1 部分 10.2 CONSTRUCT并具有以下 SPARQL 查询,该查询返回主题类型为 Homework
并且还具有事件日期的所有三元组。
CONSTRUCT { ?s ?p ?o } WHERE
{
GRAPH ?g { ?s ?p ?o } .
{ ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<http://lod.isi.edu/ontology/syllabus/Homework>
}.
{ ?s <http://lod.isi.edu/ontology/syllabus/hasEventDate> ?date}.
}
现在,我想按事件日期 ?date
的升序/降序检索结果。我尝试添加 order by
修饰符,如下所示,但 OpenRDF 工作台中存在解析错误。
CONSTRUCT { ?s ?p ?o } WHERE
{
GRAPH ?g { ?s ?p ?o } .
{ ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<http://lod.isi.edu/ontology/syllabus/Homework>
}.
{ ?s <http://lod.isi.edu/ontology/syllabus/hasEventDate> ?date}.
ORDER BY DESC(?date)
}
Encountered " "order" "ORDER "" at line 9, column 6. Was expecting one of:
"(" ... "{" ... "}" ... "[" ... <NIL> ... <ANON> ... "optional" ...
"graph" ... "minus" ... "filter" ... "true" ... "false" ... "bind" ...
"service" ... "values" ... <Q_IRI_REF> ... <PNAME_NS> ... <PNAME_LN> ...
<BLANK_NODE_LABEL> ... <VAR1> ... <VAR2> ... <INTEGER> ... <INTEGER_POSITIVE> ...
<INTEGER_NEGATIVE> ... <DECIMAL> ... <DECIMAL_POSITIVE> ...
<DECIMAL_NEGATIVE> ... <DOUBLE> ... <DOUBLE_POSITIVE> ...
<DOUBLE_NEGATIVE> ... <STRING_LITERAL1> ... <STRING_LITERAL2> ...
<STRING_LITERAL_LONG1> ... <STRING_LITERAL_LONG2> ...
最佳答案
问题是您的 ORDER BY
子句在查询中的位置不正确。它应该在结束 WHERE 子句的右括号之后:
CONSTRUCT { ?s ?p ?o }
WHERE
{
GRAPH ?g { ?s ?p ?o }
?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://lod.isi.edu/ontology/syllabus/Homework> .
?s <http://lod.isi.edu/ontology/syllabus/hasEventDate> ?date .
}
ORDER BY ASC(?date)
另请注意,您的原始查询中的几个大括号虽然不是完全错误,但却是多余的。
关于rdf - SPARQL 的 CONSTRUCT 模式中的 ORDER BY 解决方案修饰符,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22029189/