| content
| - %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 <o2a> and <o2b>, and was not requested <o3a>:
<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]]
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