%META:TOPICPARENT{name="VirtTipsAndTricksGuide"}%

---+ Can I Delete Triples containing Blank Nodes?

There are two ways to delete a particular blank node:
   1 Refer to it indirectly, using some of its properties, or
   1 Discover and refer to it by its internal "serial number" or ID (in Virtuoso, <code><nowiki>bif:iri_id_XXX</nowiki></code>, a long integer).  <i><b>Important Note</b>: IDs of bnodes will always vary from server to server, and often from run-to-run on the same server, so it is usually better to identify bnodes by properties than ID.</i>

---++ How to Delete Triples containing Blank Nodes

Assume the following sample scenario:

   1 Clear the graph:
<verbatim>
SPARQL 
  CLEAR GRAPH <http://sample/>;

Done. -- 4 msec.
</verbatim>
   1 Insert three blank nodes with two related triples each:
<verbatim>   
SPARQL 
  INSERT IN GRAPH <http://sample/> 
    { 
      []  <p>  <o1a> ,
               <o1b> .
      []  <p>  <o2a> ,
               <o2b> .
      []  <p>  <o3a> ,
               <o3b>
    };

Done. -- 15 msec.
</verbatim>
   1 Delete one pair of triples:
<verbatim>   
SPARQL WITH <http://sample/> 
  DELETE
    { ?s  ?p   ?o } 
  WHERE 
    { 
      ?s  ?p   ?o ;
          <p>  <o1a>
    }

Done. -- 7 msec.
</verbatim>
   1 Ensure that we still have two bnodes, two triple per bnode:
<verbatim>   
SPARQL 
  SELECT * 
  FROM <http://sample/> 
  WHERE 
    { 
      ?s ?p ?o 
    };

s                p        o
VARCHAR          VARCHAR  VARCHAR
_________________________________

nodeID://b10006  p        o3a
nodeID://b10006  p        o3b
nodeID://b10007  p        o2a
nodeID://b10007  p        o2b

4 Rows. -- 4 msec.
</verbatim>
   1 Every node in the Virtuoso store, whether "named" or "blank" ("unnamed"), is identified internally by a long integer:
<verbatim>   
SPARQL 
  SELECT  (<LONG::bif:iri_id_num>(?s)) AS ?s_num ,
                                          ?p     ,
                                          ?o 
  FROM <http://sample/> 
  WHERE 
    { 
      ?s  ?p  ?o 
    };

s_num                p       o
INTEGER              VARCHAR VARCHAR
_____________________________

4611686018427397910  p       o3a
4611686018427397910  p       o3b
4611686018427397911  p       o2a
4611686018427397911  p       o2b

4 Rows. -- 5 msec.
</verbatim>
   1 The integer can be converted back to internal identifier. Say, here we try to delete a triple that does not exist (even if the ID integer is valid):
<verbatim>   
SPARQL 
  DELETE FROM <http://sample/>
    { 
      `bif:iri_id_from_num(4611686018427397911)`  <p>  <o3a> 
    };

Done. -- 5 msec.
</verbatim>  
   1 Should have no effect, because the "46..11" IRI has &lt;o2a&gt; and &lt;o2b&gt;, and was not requested &lt;o3a&gt;:
<verbatim>   
SPARQL 
  SELECT * 
  FROM <http://sample/> 
  WHERE 
    { 
      ?s  ?p  ?o 
    };
s                p         o
VARCHAR          VARCHAR   VARCHAR
__________________________________

nodeID://b10006  p         o3a
nodeID://b10006  p         o3b
nodeID://b10007  p         o2a
nodeID://b10007  p         o2b

4 Rows. -- 5 msec.
</verbatim>
   1 Now let's try to delete a triple that does actually exist. Note the use of backquotes to insert an expression into the graph template:
<verbatim>   
SPARQL 
  DELETE FROM <http://sample/>
    { 
      `bif:iri_id_from_num(4611686018427397911)`  <p>  <o2a> 
    };

Done. -- 4 msec.
</verbatim>
   1 This time, there's an effect:
<verbatim>   
SPARQL 
  SELECT * 
  FROM <http://sample/> 
  WHERE 
    { 
      ?s ?p ?o 
    };
s                p        o
VARCHAR          VARCHAR  VARCHAR
_________________

nodeID://b10006  p        o3a
nodeID://b10006  p        o3b
nodeID://b10007  p        o2b

3 Rows. -- 2 msec.
</verbatim>
   1 Now we'll delete everything related to <code>nodeID://b10006</code> subject:
<verbatim>   
SPARQL 
  WITH <http://sample/> 
  DELETE 
    { 
      ?s  ?p  ?o 
    } 
  WHERE 
    { 
      ?s  ?p  ?o .
      FILTER ( ?s = bif:iri_id_from_num(4611686018427397910) )
    };

Done. -- 18 msec.
</verbatim>
   1 This should delete two of the previous three triples, leaving one remaining triple:
<verbatim>   
SQL> SPARQL 
  SELECT * 
  FROM <http://sample/> 
  WHERE 
    { 
      ?s  ?p  ?o 
    };
s                 p         o
VARCHAR           VARCHAR   VARCHAR
___________________________________

nodeID://b10007   p         o2b

1 Rows. -- 4 msec.
</verbatim>



---++Related

   * [[VirtTipsAndTricksGuide][Virtuoso Tips and Tricks Collection]]
   * [[http://docs.openlinksw.com/virtuoso/rdfsparql.html][Virtuoso Documentation]]
   * [[http://docs.openlinksw.com/virtuoso/sparqlextensions.html#rdfsparulexamples14][Deleting triples from a graph]]
   * [[VirtTipsAndTricksGuideDeleteLargeGraphs][Deleting triples from a "Large" graph]]