Query pattern for SDO_RDF_MATCH

Question

What form of query can be found in the first SDO_RDF_MATCH function parameter?
In SPARQL it is possible to use in OPTIONAL keyword, for example
SELECT ?x ?y ?z
?x test:value ?y OPTIONAL {  ?y test:hasIncome ?z }
I will be given in the result the records which has both triples, but also those for which te second triple is not set. Is it possible to get the same effect in Oracle?
Thanks for answer.

Answer 1

We do not yet support the use of OPTIONAL in the query pattern, but the query can be expressed by calling SDO_RDF_MATCH twice and using an outer join.
For example, consider the example in the documentation (the 'family' model). The following query will select subjects of type 'Male', including those who do not have an address set.
Melli
SELECT t1.x Male, t2.y Address
FROM TABLE(SDO_RDF_MATCH(
'(?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> :Male)',
SDO_RDF_Models('family'),
NULL,
SDO_RDF_Aliases(SDO_RDF_Alias('','http://www.example.org/family/')),
null)) t1,
TABLE(SDO_RDF_MATCH(
'(?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> :Male)
(?x :address ?y)',
SDO_RDF_Models('family'),
NULL,
SDO_RDF_Aliases(SDO_RDF_Alias('','http://www.example.org/family/')),
null)) t2
where t1.x=t2.x (+)
;