获取 relYear 或在 dbpedia 单曲数据中发布而不记录重复

Question

Here 是以下查询的浏览输出，用于尝试获取广告牌前 100 名的单曲：

PREFIX prop: <http://dbpedia.org/property/>
PREFIX ont: <http://dbpedia.org/ontology/>

SELECT DISTINCT ?page, ?artist, ?relYear, ?released, ?runTime WHERE {
  ?page dct:subject dbc:Billboard_Hot_100_number-one_singles .
  OPTIONAL {?page prop:artist ?artist}.
  OPTIONAL {?page prop:relyear ?relYear}.
  OPTIONAL {?page prop:released ?released}.
  OPTIONAL {?page ont:runtime ?runTime}
}

我放了 relYear 并发布了，因为有些单曲有一个，有些有另一个，有些两个都有，有些两个都没有。

如果您查看输出，它会重复行：一行是 relYear，第二行是 released。我想要 SQL COALESCE(released, relYear) 之类的东西，即将存在的 (released, relYear) 的第一个元素放在一行中。

我该怎么做？

P.S。我对 artist 和 musicalArtist 等有同样的问题，所以行最终疯狂地增加。

P.P.S。看了this，但没有帮助。

Answer 1

基本上你已经知道答案了，用COALESCE:

PREFIX prop: <http://dbpedia.org/property/>
PREFIX ont: <http://dbpedia.org/ontology/>

SELECT DISTINCT ?page ?artist (coalesce(?relYear, ?released) as ?releaseYear) ?runTime WHERE {
  ?page dct:subject dbc:Billboard_Hot_100_number-one_singles .
  OPTIONAL {?page prop:artist ?artist}.
  OPTIONAL {?page prop:relyear ?relYear}.
  OPTIONAL {?page prop:released ?released}.
  OPTIONAL {?page ont:runtime ?runTime}
}

但是，我想您已经知道，同一首单曲可以有多个版本，由不同的艺术家完成并以不同的版本完成，因此，您可能会为同一首单曲获得多行。作为一个极端的例子，看看 Total_Eclipse_of_the_Heart

+------------------------------+--------------------------------+-------------+---------+
|             page             |             artist             | releaseYear | runTime |
+------------------------------+--------------------------------+-------------+---------+
| :Total_Eclipse_of_the_Heart  | "Bonnie Tyler"^^rdf:langString |        1983 |   180.0 |
| :Total_Eclipse_of_the_Heart  | "Nicki French"^^rdf:langString |        1983 |   180.0 |
| :Total_Eclipse_of_the_Heart  | "Bonnie Tyler"^^rdf:langString |        1995 |   180.0 |
| :Total_Eclipse_of_the_Heart  | "Nicki French"^^rdf:langString |        1995 |   180.0 |
| :Total_Eclipse_of_the_Heart  | "Bonnie Tyler"^^rdf:langString |        2012 |   180.0 |
| :Total_Eclipse_of_the_Heart  | "Nicki French"^^rdf:langString |        2012 |   180.0 |
| :Total_Eclipse_of_the_Heart  | "Bonnie Tyler"^^rdf:langString |        1983 |   230.0 |
| :Total_Eclipse_of_the_Heart  | "Nicki French"^^rdf:langString |        1983 |   230.0 |
| :Total_Eclipse_of_the_Heart  | "Bonnie Tyler"^^rdf:langString |        1995 |   230.0 |
| :Total_Eclipse_of_the_Heart  | "Nicki French"^^rdf:langString |        1995 |   230.0 |
| :Total_Eclipse_of_the_Heart  | "Bonnie Tyler"^^rdf:langString |        2012 |   230.0 |
| :Total_Eclipse_of_the_Heart  | "Nicki French"^^rdf:langString |        2012 |   230.0 |
| ...                          | ...                            |         ... |     ... |
+------------------------------+--------------------------------+-------------+---------+

你可以做一些类似group by here, to get at least for each artist only one row, e.g. in combination with group_concat or sample

的事情

获取 relYear 或在 dbpedia 单曲数据中发布而不记录重复

get relYear or released in dbpedia singles data without record duplication

rdf

sparql

dbpedia