Functional Dependencies

Notation

In Database theory: <math>\{A,B\}\to \{C,D\}</math> is abbreviated to: <math>AB\to CD</math>

Example

9 single entries for 2022 sorted by social media followers

query

# WF 2022-06-08
# Singles published in 2022
SELECT
?single ?language ?collectionId ?collection ?collectionType ?performerId ?performer ?followerCount ?youtubeVideoId  (year(?publicationDate) as ?publicationYear)
WHERE
{
  # instanceof
  ?singleId wdt:P31 wd:Q134556. # Must be of a single
  ?singleId rdfs:label ?single.
  FILTER(LANG(?single)='en')

  #https://www.wikidata.org/wiki/Property:P361 - part of / ist Teil von
  ?singleId wdt:P361 ?collectionId.
  ?collectionId rdfs:label ?collection.
  FILTER(LANG(?collection)='en')

  # https://www.wikidata.org/wiki/Property:P407 language/ Sprache des Werkes
  ?singleId wdt:P407 ?languageId.
  ?languageId rdfs:label ?language.
  FILTER(LANG(?language)='en')

  # https://www.wikidata.org/wiki/Property:P1651 YouTube-Video-Kennung
  ?singleId wdt:P1651 ?youtubeVideoId.

  ?collectionId wdt:P31 ?collectionTypeId.
  ?collectionTypeId rdfs:label ?collectionType.
  FILTER(LANG(?collectionType)='en').

  # https://www.wikidata.org/wiki/Property:P175 Performer /Interpret
  ?singleId wdt:P175 ?performerId.
  ?performerId rdfs:label ?performer
  FILTER(LANG(?performer)='en')

  # https://www.wikidata.org/wiki/Property:P8687 followers / Follower
  #{
     #SELECT (max(?followerCount) as ?follower)
     #WHERE {
     ?performerId wdt:P8687 ?followerCount.
     #}
     #GROUP BY ?performerId
  #}
  #https://www.wikidata.org/wiki/Property:P577 Publication date / Veröffentlichungsdatum
  ?singleId wdt:P577 ?publicationDate.
  FILTER(year(?publicationDate) = 2022).
} ORDER BY  DESC(?followerCount)
LIMIT 9

[None/#%23%20WF%202022-06-08%0A%23%20Singles%20published%20in%202022%0ASELECT%0A%3Fsingle%20%3Flanguage%20%3FcollectionId%20%3Fcollection%20%3FcollectionType%20%3FperformerId%20%3Fperformer%20%3FfollowerCount%20%3FyoutubeVideoId%20%20%28year%28%3FpublicationDate%29%20as%20%3FpublicationYear%29%0AWHERE%0A%7B%0A%20%20%23%20instanceof%0A%20%20%3FsingleId%20wdt%3AP31%20wd%3AQ134556.%20%23%20Must%20be%20of%20a%20single%0A%20%20%3FsingleId%20rdfs%3Alabel%20%3Fsingle.%0A%20%20FILTER%28LANG%28%3Fsingle%29%3D%27en%27%29%0A%0A%20%20%23https%3A//www.wikidata.org/wiki/Property%3AP361%20-%20part%20of%20/%20ist%20Teil%20von%0A%20%20%3FsingleId%20wdt%3AP361%20%3FcollectionId.%0A%20%20%3FcollectionId%20rdfs%3Alabel%20%3Fcollection.%0A%20%20FILTER%28LANG%28%3Fcollection%29%3D%27en%27%29%0A%0A%20%20%23%20https%3A//www.wikidata.org/wiki/Property%3AP407%20language/%20Sprache%20des%20Werkes%0A%20%20%3FsingleId%20wdt%3AP407%20%3FlanguageId.%0A%20%20%3FlanguageId%20rdfs%3Alabel%20%3Flanguage.%0A%20%20FILTER%28LANG%28%3Flanguage%29%3D%27en%27%29%0A%0A%20%20%23%20https%3A//www.wikidata.org/wiki/Property%3AP1651%20YouTube-Video-Kennung%0A%20%20%3FsingleId%20wdt%3AP1651%20%3FyoutubeVideoId.%0A%0A%20%20%3FcollectionId%20wdt%3AP31%20%3FcollectionTypeId.%0A%20%20%3FcollectionTypeId%20rdfs%3Alabel%20%3FcollectionType.%0A%20%20FILTER%28LANG%28%3FcollectionType%29%3D%27en%27%29.%0A%0A%20%20%23%20https%3A//www.wikidata.org/wiki/Property%3AP175%20Performer%20/Interpret%0A%20%20%3FsingleId%20wdt%3AP175%20%3FperformerId.%0A%20%20%3FperformerId%20rdfs%3Alabel%20%3Fperformer%0A%20%20FILTER%28LANG%28%3Fperformer%29%3D%27en%27%29%0A%0A%20%20%23%20https%3A//www.wikidata.org/wiki/Property%3AP8687%20followers%20/%20Follower%0A%20%20%23%7B%0A%20%20%20%20%20%23SELECT%20%28max%28%3FfollowerCount%29%20as%20%3Ffollower%29%0A%20%20%20%20%20%23WHERE%20%7B%0A%20%20%20%20%20%3FperformerId%20wdt%3AP8687%20%3FfollowerCount.%0A%20%20%20%20%20%23%7D%0A%20%20%20%20%20%23GROUP%20BY%20%3FperformerId%0A%20%20%23%7D%0A%20%20%23https%3A//www.wikidata.org/wiki/Property%3AP577%20Publication%20date%20/%20Ver%C3%B6ffentlichungsdatum%0A%20%20%3FsingleId%20wdt%3AP577%20%3FpublicationDate.%0A%20%20FILTER%28year%28%3FpublicationDate%29%20%3D%202022%29.%0A%7D%20ORDER%20BY%20%20DESC%28%3FfollowerCount%29%0ALIMIT%209%0A try it!]

result

single	language	collectionId	collection	collectionType	performerId	performer	followerCount	youtubeVideoId	publicationYear
Let Somebody Go	English	http://www.wikidata.org/entity/Q107597380	Music of the Spheres	album	http://www.wikidata.org/entity/Q83287	Selena Gomez	65629044	EptPhiK_q0E	2022
As It Was	English	http://www.wikidata.org/entity/Q111343757	Harry's House	album	http://www.wikidata.org/entity/Q3626966	Harry Styles	36156370	H5v3kku4y6Q	2022
Let Somebody Go	English	http://www.wikidata.org/entity/Q107597380	Music of the Spheres	album	http://www.wikidata.org/entity/Q45188	Coldplay	23541189	EptPhiK_q0E	2022
Bam Bam	English	http://www.wikidata.org/entity/Q56071495	Camila Cabello singles discography	singles discography	http://www.wikidata.org/entity/Q47447	Ed Sheeran	17661915	-8VfKZCOo_I	2022
Bam Bam	English	http://www.wikidata.org/entity/Q111083420	Familia	album	http://www.wikidata.org/entity/Q47447	Ed Sheeran	17661915	-8VfKZCOo_I	2022
Sacrifice	English	http://www.wikidata.org/entity/Q110400486	Dawn FM	album	http://www.wikidata.org/entity/Q2121062	The Weeknd	15549868	VafTMsrnSTU	2022
Out of Time	English	http://www.wikidata.org/entity/Q110400486	Dawn FM	album	http://www.wikidata.org/entity/Q2121062	The Weeknd	15549868	2fDzCWNS3ig	2022
Bam Bam	English	http://www.wikidata.org/entity/Q56071495	Camila Cabello singles discography	singles discography	http://www.wikidata.org/entity/Q18810940	Camila Cabello	12717885	-8VfKZCOo_I	2022
Bam Bam	English	http://www.wikidata.org/entity/Q111083420	Familia	album	http://www.wikidata.org/entity/Q18810940	Camila Cabello	12717885	-8VfKZCOo_I	2022

Links

• https://en.wikipedia.org/wiki/Category:Database_theory
• https://en.wikipedia.org/wiki/Functional_dependency
• https://en.wikipedia.org/wiki/Database_normalization
• https://en.wikipedia.org/wiki/Second_normal_form
• https://en.wikipedia.org/wiki/Third_normal_form
• https://en.wikipedia.org/wiki/Candidate_key
• https://en.wikipedia.org/wiki/Surrogate_key
• https://stackovemahrflow.com/questions/tagged/functional-dependencies