...

SELECT * from named <https://unstats.un.org/classifications/CPC/v2.1/> {
  GRAPH ?g { ?s ?p ?o }.
}

Get al items in 

SELECT ?collection_code ?concept_code ?concept_label  WHERE {
    ?collection skos:notation ?collection_code . FILTER (str(?collection_code)='fisheries') .
    ?collection skos:member ?concept .
    ?concept skos:notation ?concept_code .
    ?concept skos:prefLabel ?concept_label .
}

...

SELECT ?s  
WHERE {
  ?s rdf:type skos:ConceptScheme .
}

On skos:Collections

Get all members of skos:collection "fisheries"

SELECT ?collection_code ?concept_code ?concept_label  WHERE {
    ?collection skos:notation ?collection_code . FILTER (str(?collection_code)='fisheries') .
    ?collection skos:member ?concept .
    ?concept skos:notation ?concept_code .
    ?concept skos:prefLabel ?concept_label .
}

Manipulate data

Add a triple to all skos:Concept in a graph  

INSERT
{ GRAPH <graph_name>
 {?s prefix:property <property_value> } }
WHERE {
    ?s rdf:type skos:Concept .

}