OPTIONAL

Understanding OPTIONAL

Without OPTIONAL, SPARQL requires all patterns to match. If an entity lacks a property, it's excluded from results. OPTIONAL lets you request data that might not exist—if it does, you get it; if not, the result row still appears with that variable unbound.

Basic OPTIONAL Examples

SELECT ?person ?personLabel ?birth ?death
WHERE {
  ?person wdt:P31 wd:Q5 ;
          wdt:P106 wd:Q901 ;
          wdt:P569 ?birth .
  OPTIONAL { ?person wdt:P570 ?death . }
  SERVICE wikibase:label { bd:serviceParam wikibase:language "en". }
}
LIMIT 20

This query finds scientists with their birth dates (required) and death dates (optional). Living scientists appear in results with an empty ?death value. Without OPTIONAL, only deceased scientists would be returned.

SELECT ?city ?cityLabel ?population
WHERE {
  ?city wdt:P31 wd:Q515 ;
        wdt:P17 wd:Q183 .
  OPTIONAL { ?city wdt:P1082 ?population . }
  SERVICE wikibase:label { bd:serviceParam wikibase:language "en". }
}
LIMIT 30

Not all cities in Wikidata have population data recorded. Using OPTIONAL ensures we get all German cities, showing population when available and leaving it empty when not recorded.

Multiple OPTIONAL Clauses

SELECT ?author ?authorLabel ?birthPlaceLabel ?deathPlaceLabel
WHERE {
  ?author wdt:P31 wd:Q5 ;
          wdt:P106 wd:Q36180 .
  OPTIONAL { ?author wdt:P19 ?birthPlace . }
  OPTIONAL { ?author wdt:P20 ?deathPlace . }
  SERVICE wikibase:label { bd:serviceParam wikibase:language "en". }
}
LIMIT 25

Multiple OPTIONAL clauses are independent—each is tried separately. An author might have a birth place but no death place, or vice versa, or neither, or both. All combinations appear in the results.

OPTIONAL with FILTER

SELECT ?movie ?movieLabel ?budget
WHERE {
  ?movie wdt:P31 wd:Q11424 ;
         wdt:P577 ?date .
  FILTER(YEAR(?date) = 2020)
  OPTIONAL { ?movie wdt:P2130 ?budget . }
  SERVICE wikibase:label { bd:serviceParam wikibase:language "en". }
}
LIMIT 30

The FILTER applies to required patterns, while OPTIONAL values are still included when available. This gets all 2020 films, showing budget data only for films where it's recorded. Use BOUND() with FILTER to check if optional values exist.

Key Entities Used in Examples