Tourism overnights per season

PREFIX sdmx-measure: <http://purl.org/linked-data/sdmx/2009/measure#> 
PREFIX sdmx-dimension: <http://purl.org/linked-data/sdmx/2009/dimension#> 
PREFIX sdmx-attribute: <http://purl.org/linked-data/sdmx/2009/attribute#> 
PREFIX property: <http://rdfdata.eionet.europa.eu/eurostat/property#> 
PREFIX geo: <http://dd.eionet.europa.eu/vocabulary/eurostat/geo/>
PREFIX unit: <http://dd.eionet.europa.eu/vocabulary/eurostat/unit/>
PREFIX nace_r2: <http://dd.eionet.europa.eu/vocabulary/eurostat/nace_r2/>
PREFIX indic_to: <http://dd.eionet.europa.eu/vocabulary/eurostat/indic_to/>

SELECT 
?quarter
?date
?ugeo
sum(?obsValue) as ?obsValue
{{
  SELECT
    bif:either( month(?date) in (1,2,3), 'Quarter 1', 
    bif:either( month(?date) in (4,5,6), 'Quarter 2', 
    bif:either( month(?date) in (7,8,9), 'Quarter 3', 'Quarter 4'))) as ?quarter
    year(?date) as ?date
    bif:either(?geo = geo:DE, 'Germany', ?ugeo) as ?ugeo
    sum(?obsValue) as ?obsValue
  WHERE {
    GRAPH <http://rdfdata.eionet.europa.eu/eurostat/data/tour_occ_nim.rdf.gz> 
    {
      _:tour_occ_nim sdmx-dimension:timePeriod ?date .
      FILTER (year(?date) >= 2000)
      _:tour_occ_nim sdmx-dimension:refArea ?geo . 
      _:tour_occ_nim property:indic_to indic_to:B006 . 
      _:tour_occ_nim sdmx-attribute:unitMeasure unit:NR . 
      _:tour_occ_nim property:nace_r2 nace_r2:I551-I553 . 
      _:tour_occ_nim sdmx-measure:obsValue ?obsValue .
    }
    ?geo skos:exactMatch ?eeauri .
    ?eeauri skos:inScheme <http://dd.eionet.europa.eu/vocabulary/common/countries/> .
    ?eeauri rdfs:label ?ugeo .
  }
}}