Select literal in SPARQL? - sparql

Question

I want to construct a SPARQL query populated with values I'm setting as literals.
e.g.
SELECT 'A', 'B', attribute
FROM
TABLE
Would return a table that might look like this:
A | B | attribute
-------|---------|--------------
A | B | Mary
A | B | has
A | B | a
A | B | little
A | B | lamb
What I want to do is run a query like this to get all the object types in a triplestore:
select distinct ?o ("class" as ?item_type)
where {
?s rdf:type ?o.
}
and then (ideally) UNION it with a second query that pulls out all the distinct predicate values:
select distinct ?p ("predicate" as ?item_type)
where {
?s ?p ?o.
}
the results of which might look like:
item | item_type
-----------------|-----------------
a_thing | class
another_thing | class
a_relation | predicate
another_relation | predicate
But a UNION in SPARQL only links in an additional where clause, which means I can't specify the item_type literal I want to inject into my results-set.

Answer 1

I think the following should get you what you want:
SELECT DISTINCT ?item ?item_type
WHERE {
{ ?s a ?item .
BIND("class" AS ?item_type)
}
UNION
{ ?s ?item ?o
BIND("predicate" AS ?item_type)
}
}