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
result
A | B | C | D | E | F | G | H | I | J |
---|---|---|---|---|---|---|---|---|---|
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 |
Functional Dependencies
The functional dependencies in this example are derived from the structure of the SPARQL query
- [math]A\to BCFIJ[/math]
- [math]C\to DE[/math]
- [math]F\to GH[/math]
[math]R={{\{A,B,C,D,E,F,G,H,I,J\}},{A\to BCFIJ,C\to DE,F\to GH}}[/math]
Synthesis
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/First_normal_form
- https://en.wikipedia.org/wiki/Second_normal_form
- https://en.wikipedia.org/wiki/Third_normal_form
- https://en.wikipedia.org/wiki/Boyce%E2%80%93Codd_normal_form
- https://en.wikipedia.org/wiki/Lossless_join_decomposition
- https://en.wikipedia.org/wiki/Candidate_key
- https://en.wikipedia.org/wiki/Surrogate_key
- https://stackoverflow.com/questions/tagged/functional-dependencies