PREFIX dc: <http://purl.org/dc/elements/1.1/>
PREFIX x: <http://example.org/ns#>
SELECT ?title ?price
WHERE
{ ?book dc:title ?title .
OPTIONAL
{ ?book x:price ?price } .
FILTER (?price < 15) .
}
PREFIX dc: <http://purl.org/dc/elements/1.1/>
PREFIX x: <http://example.org/ns#>
SELECT ?title ?price
WHERE
{ ?book dc:title ?title .
OPTIONAL
{ ?book x:price ?price } .
FILTER (?price < 15) .
}