SPARQL query of Turtle data returns no rows when using skos:prefLabel

Question

I'm trying to query PubChem disease data from their Turtle file in GraphDb. The standard query returns all the ?s ?p ?o rows as expected. But I just want the ?s and skos:prefLabel.

Example disease data: https://pubchem.ncbi.nlm.nih.gov/rest/rdf/disease/DZID8805.html

This returns 100 rows as expected. One row shown below.

select * 
FROM <http://localhost:7200/diseases>  
where { 
   ?s ?p ?o .
} limit 100 

disease:DZID1364 / rdf:type / obo:DOID_4

I tried various queries with no results. This is the latest attempt. It's from a named graph that contains all the data locally. I'm new to SPARQL and RDF and this just looks like it should work.

prefix skos: <http://www.w3.org/2004/02/skos/core#/>  
prefix disease: <http://rdf.ncbi.nlm.nih.gov/pubchem/disease/>

SELECT ?label
FROM <http://localhost:7200/diseases>  
WHERE { 
    ?disease skos:prefLabel ?label
} limit 100

Expected row below.

disease:DZID1364 / White platelet syndrome

From TTL file:

disease:DZID1364  skos:prefLabel  "White platelet syndrome" .

Answer 1

As stated by @UninformedUser, I removed the trailing / from the skos prefix declaration and it resolved the issue.