Group concat not working

Question

I\'ve written a query without using group_concat and get 9 rows returned, one row for each occupation that Einstein held.

When I add group_concat on the occupation c

Answer 1

The rough idea is to use dedicated SPARQL triple patterns for getting the label instead of the "label service":

SELECT ?item ?itemLabel ?genderLabel (GROUP_CONCAT(?occupationLabel) AS ?occupations)
WHERE {
  ?item wdt:P31 wd:Q5.
  ?item ?label "Albert Einstein"@en.
  ?item wdt:P21 ?gender .
  OPTIONAL {
    ?item wdt:P106 ?occupation .
  }
  SERVICE wikibase:label { 
    bd:serviceParam wikibase:language "en". 
    ?item rdfs:label ?itemLabel . 
    ?gender rdfs:label ?genderLabel . 
    ?occupation rdfs:label ?occupationLabel 
  }
}
GROUP BY ?item ?itemLabel ?genderLabel