sparql - SPARQL 查询中两个选择的并集

Question

我想做一些类似的事情

{
    SELECT ?page, "A" AS ?type WHERE 
    {
         ?s rdfs:label "Microsoft"@en;
            foaf:page ?page
    }
}
UNION
{
    SELECT ?page, "B" AS ?type WHERE 
    {
         ?s rdfs:label "Apple"@en;
            foaf:page ?page
    }
}

但这会产生语法错误。如何在 SPARQL 中联合两个选择查询？

Answer 1

你可以像这样联合它们:

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>

SELECT * WHERE
{ 
{
    SELECT ?page ("A" AS ?type) WHERE 
    {
         ?s rdfs:label "Microsoft"@en;
            foaf:page ?page
    }
}
UNION
{
    SELECT ?page ("B" AS ?type) WHERE 
    {
         ?s rdfs:label "Apple"@en;
            foaf:page ?page
    }
}
}

(检查 SPARQL validator )

但是，我认为在这种情况下您根本不需要子查询。例如:

PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>

SELECT ?page ?type WHERE
{
    ?s foaf:page ?page .
    { ?s rdfs:label "Microsoft"@en . BIND ("A" as ?type) }
    UNION
    { ?s rdfs:label "Apple"@en . BIND ("B" as ?type) }
}