{ }
#title: Notable books on linked data, semantic technologies, and semantic knowledge graphs
SELECT DISTINCT ?book ?title (GROUP_CONCAT (DISTINCT ?author; SEPARATOR = ", ") AS ?authors) ?pubDate
{
VALUES ?book {wd:Q17744504 wd:Q17744476 wd:Q61718117 wd:Q59784970 wd:Q17744339 wd:Q51601248 wd:Q17744488 wd:Q27942623 wd:Q108378522 wd:Q110549106 wd:Q109673922 wd:Q93431614}
?book wdt:P1476 ?title.
OPTIONAL {?book (wdt:P50/rdfs:label)|(wdt:P98/rdfs:label)|wdt:P2093 ?author
FILTER (LANG(?author)=""||LANG(?author)="en")}
OPTIONAL {?book wdt:P577 ?pubDate}
}
GROUP BY ?book ?title ?pubDate
#Wikidata #Query #II #OPTIONAL#note: this is a snippet, not a valid query
VALUES (?x ?y ?z) {(:URI1 "ex" 1) (:URI2 "wye" 2) (:URI3 "zed" UNDEF)}
?z
, shown by the keyword UNDEF
()
can be omitted for single values as in the example above
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