Suppose the following situation:
Using SQL you can execute the following:
SQL> SPARQL
DELETE FROM rdf_quad
WHERE s = iri_to_id ('http://linkeddata.uriburner.com/about/id/entity/http/twitter.com/kidehen')
AND o = iri_to_id ('http://purl.org/ontology/bibo/Document')
AND p = iri_to_id ('http://www.w3.org/1999/02/22-rdf-syntax-ns#type');