***UNCHECKED*** Antw: Re: How to use ORDER BY in a query built by the ARQ API?

[Andreas Kahl]

Rob, 

Thanks a lot for your help. Now I can generate my complete query with
the ARQ API (I simplified the initial example in my first question): 

PREFIX  skos: <http://www.w3.org/2004/02/skos/core#>

SELECT DISTINCT  *
WHERE
  { 

   ?id  skos:broader <URI>
   OPTIONAL
        { 

       ?id skos:prefLabel|skos:altLabel ?label
               FILTER langMatches("en", lang(?label))
   }
   OPTIONAL
   { ?id  skos:prefLabel  ?label}
  }
ORDER BY (?id)

The SelectBuilder is really great and I would like to use it. Only at
the moment I struggle with creating the first OPTIONAL block, which
contains a FILTER applied only inside this block. How can I create such
a block? I tried addSubQuery with another SelectBuilder or WhereBuilder,
but both add an unnecessary WHERE inside the OPTIONAL - rendering the
query syntactically incorrect. Is the querybuilder API too limited for
that, or am I missing something?

Please find both versions of the code (ARQ API and Querybuilder) as Java
code snippets in the attachment. (The ARQ version is working correctly)


Best Regards
Andreas



>>> Rob Vesse <rve...@dotnetrdf.org> 18.09.18 17.30 Uhr >>>
Use one of the .addOrderBy() methods on the Query object -
https://jena.apache.org/documentation/javadoc/arq/org/apache/jena/query/Query.html#addOrderBy-org.apache.jena.sparql.expr.Expr-int-

 

If you are building lots of queries programmatically the higher level
Query Builder API may be more user friendly -
https://jena.apache.org/documentation/extras/querybuilder/index.html

 

Rob

 

From: Andreas Kahl <k...@bsb-muenchen.de>
Reply-To: <users@jena.apache.org>
Date: Tuesday, 18 September 2018 at 07:55
To: <users@jena.apache.org>
Subject: How to use ORDER BY in a query built by the ARQ API?

 

Hello everyone, 

how is it possible to build a query like: 
SELECT DISTINCT  * WHERE
  { 
    ?s  skos:broader  ?o

  } 

ORDER BY ?s

 

with the Jena ARQ API (org.apache.jena.sparql.syntax.*)

 

The first part would be achieved by: 

 

final ElementTriplesBlock baseCriteria = new ElementTriplesBlock();
baseCriteria.addTriple(

     new Triple(

         Var.alloc("s"),

         NodeFactory.createURI("skos:broader"),

         Var.alloc("o")

     )

);

 

I can add this to an ElementGroup, but which Java Type shall be used to
gernerate ORDER BY ?s ?

 

Thanks & Best Regards

Andreas