sparql 如何将子查询转换为另一个查询

Question

我有这个数据

@prefix : <http://test.example/> .

:alice :likes :beethoven.
:alice :likes :verdi.
:sofia :likes :beethoven.
:sofia :likes :verdi.
:sofia :likes :rossini.
:ania :likes :verdi.
:ania :likes :beethoven.
:ania :likes :david.
:david :likes :ania.
:david :likes :beethoven.
:david :likes :verdi.
:antonino :likes :verdi.
:antonino :likes :mozart.
:weirdo :likes :katyperry.
:beethoven a :recommendable.
:verdi a :recommendable.
:rossini a :recommendable.
:katyperry a :recommendable.
:mozart a :recommendable.

然后我进行查询以获取与特定用户喜欢相同商品的用户

select ?anotherUser (COUNT(?anotherItem) as ?countOfItems) WHERE {
  values ?user {:ania}
  ?anotherUser :likes ?anotherItem.
  filter (?anotherUser != ?user)
  filter exists {?user :likes ?anotherItem}
}group by ?anotherUser
order by desc(?countOfItems)

现在我想获取这些用户喜欢的项目（但当然没有他们与该特定用户共享的项目 (:ania)）

我知道我必须在另一个中包含一个查询，我自己尝试了很多但没有成功，你能帮忙吗？

Answer 1

now I want to get the items that these users like (but of course without the items that they share with that specific user (:ania))

I know I have to include a query inside the other, I tried a lot myself but no success, could you help please?

我认为要牢记的主要事情是子查询是最先评估的，即查询是从最内层开始评估的，到最外层。

所以下面的查询：

prefix : <http://test.example>
select distinct ?user ?anotherUser ?item WHERE {
  ?anotherUser :likes ?item.
  filter not exists {?user :likes ?item}
  {select ?user ?anotherUser where {
    values ?user {:ania}
    ?anotherUser :likes ?anotherItem.
    filter (?anotherUser != ?user)
    filter exists {?user :likes ?anotherItem}
  }}
}

将产生结果：

----------------------------------
| user  | anotherUser | item     |
==================================
| :ania | :sofia      | :rossini |
| :ania | :antonino   | :mozart  |
| :ania | :david      | :ania    |
----------------------------------

你问的是哪个？

sparql 如何将子查询转换为另一个查询

sparql how to sub query into another query

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