A SPARQL expression can contain calls to Virtuoso/PL functions and built-in SQL functions in both the WHERE clause and in the result set. Two namespace prefixes, bif and sql are reserved for these purposes. When a function name starts with the bif: namespace prefix, the rest of the name is treated as the name of a SQL BIF (Built-In Function). When a function name starts with the sql: namespace prefix, the rest of the name is treated as the name of a Virtuoso/PL function owned by DBA with database qualifier DB, e.g. sql:example(...) is converted into DB.DBA."example"(...) .

In both cases, the function receives arguments in SQL format ('SQL valmode') and also returns the result in SQL format. The SPARQL compiler will automatically add code for format conversion into the resulting SQL code so SQL functions can be used even if define output:valmode 'LONG' forces the use of RDF representation in the result set.

SQL>create procedure DB.DBA.ComposeInfo (
  in pname varchar,
  in pnick varchar := '',
  in pbox  varchar := '')
{
   declare ss varchar;
   ss := concat(pname, ' ', pnick, ' ', pbox);
   ss := rtrim (ss, ' ');
   return ss;

};
Done. -- 0 msec.

SQL>SPARQL
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
SELECT (sql:ComposeInfo (?name, ?nick, ?box))
FROM <http://www.w3.org/People/Berners-Lee/card>
WHERE
  {
    ?s rdf:type foaf:Person .
    optional{?s foaf:name ?name }.
    optional{?s foaf:nick ?nick }.
    optional{?s foaf:box ?box }.
    filter (?nick like '%TimBL%') .
  };
callret-0
VARCHAR
_______________________________________________________________________________

Timothy Berners-Lee TimBL

1 Rows. -- 30 msec.
SQL>SPARQL
SELECT DISTINCT ?cityUri ?cityName (sql:BEST_LANGMATCH (?cityName, 'en, en-gb;q=0.8, fr;q=0.7, *;q=0.1', '')) as ?bestCityName
WHERE
  {
    ?cityUri ?predicate ?value.
    ?cityUri a <http://dbpedia.org/ontology/City>.
    ?value bif:contains "London".
    OPTIONAL
      {
        ?cityUri rdfs:label ?cityName
      }
  };

cityUri                                              cityName                      bestCityName
ANY                                                  ANY                                 ANY
______________________________________________________________________________________________________________
http://dbpedia.org/resource/Anerley                      Anerley                             Anerley
http://dbpedia.org/resource/Felixstowe               Felixstowe                    Felixstowe
http://dbpedia.org/resource/Chesham                      Chesham                             Chesham
http://dbpedia.org/resource/Stratford%2C_London      Stratford, London             Stratford, London
http://dbpedia.org/resource/Ashford%2C_Surrey          Ashford (Surrey)  A           shford (Surrey)
http://dbpedia.org/resource/Newmarket%2C_Suffolk           Newmarket (Suffolk)           Newmarket (Suffolk)
http://dbpedia.org/resource/North_Rhine-Westphalia       Renania d'o Norte-Westfalia     Renania d'o Norte-Westfalia
http://dbpedia.org/resource/West_Bromwich                  West Bromwich                       West Bromwich
....

SQL>SPARQL
SELECT *
FROM <http://www.w3.org/people#>
WHERE { ?s ?p ?o . ?o bif:contains '"Timo*"'};
s                                               p                                     o
VARCHAR                                         VARCHAR                               VARCHAR
_______________________________________________________________________________

 http://www.w3.org/People/Berners-Lee/card#i    http://xmlns.com/foaf/0.1/name        Timothy Berners-Lee
 http://www.w3.org/People/Berners-Lee/card#i    http://xmlns.com/foaf/0.1/givenname   Timothy

2 Rows. -- 2 msec.