select all triples, indicating named graph if relevant

Question

Let's say I make the following insertions into my GraphDB 8.3 triplestore:

PREFIX : <http://example.com/>
insert data { :hello a :word }

and

PREFIX : <http://example.com/>
insert data { graph :farewells { :goodbye a :word }}

now, if I ask

select * where {
    graph ?g {
        ?s ?p ?o .
    } 
}

I only get

+--------------------------------+------------------------------+---------------------------------------------------+---------------------------+
|               ?g               |              ?s              |                        ?p                         |            ?o             |
+--------------------------------+------------------------------+---------------------------------------------------+---------------------------+
| <http://example.com/farewells> | <http://example.com/goodbye> | <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> | <http://example.com/word> |
+--------------------------------+------------------------------+---------------------------------------------------+---------------------------+

I can obviously get both "triples about words" with the following, but then the named-graph membership is not shown

select * { ?s ?p ?o }

How can I write a query that retrieves both triples about words and indicates that { :goodbye a :word } comes from graph :farewells ?

Answer 1

In case you use have to use implicit triples in other part of the query, and in case a FILTER NOT EXISTS causes performance issues.

Then you can query what you inserted without graph clause with GRAPH <http://rdf4j.org/schema/rdf4j#nil>

In your example, you could use the query:

SELECT * 
WHERE {
   { GRAPH ?g { ?s ?p ?o } }
   UNION { GRAPH <http://rdf4j.org/schema/rdf4j#nil> { ?s ?p ?o } }
}

returns:

+------------------------------------+----------+-----------+-------+
| ?g                                 | ?s       | ?p        | ?o    |
+------------------------------------+----------+-----------+-------+
|                                    | :hello   | rdf:type  | :word |
| :farewells                         | :goodbye | rdf:type  | :word |
+------------------------------------+----------+-----------+-------+

At least it works in my free graphDB GraphDB 10.2.0 • RDF4J 4.2.2

Edit: I found one "better":

SELECT * 
WHERE {
    VALUES ?g {UNDEF <http://rdf4j.org/schema/rdf4j#nil>}
    GRAPH ?g { ?s ?p ?o } 
}

It returns:

+------------------------------------+----------+-----------+-------+
| ?g                                 | ?s       | ?p        | ?o    |
+------------------------------------+----------+-----------+-------+
|  rdf4j:nil                         | :hello   | rdf:type  | :word |
| :farewells                         | :goodbye | rdf:type  | :word |
+------------------------------------+----------+-----------+-------+