SPARQL group by 和 order by : not ordered

Question

我跟进 query其中 schema.org 数据库用于查找类的子级数量 - 作为比我的应用程序更简单的数据库。我想按字母顺序连接 child 的名字。查询:

prefix schema:  <http://schema.org/>
prefix rdfs:    <http://www.w3.org/2000/01/rdf-schema#>

select    ?child  (group_concat (?string) as ?strings) 
where {
  ?child  rdfs:subClassOf schema:Event .
     ?grandchild rdfs:subClassOf ?child .
  bind (strafter(str(?grandchild), "http://schema.org/") as ?string)
}   group by ?child  order by asc(?string)
limit 20 

给

schema:PublicationEvent   "OnDemandEvent BroadcastEvent"
schema:UserInteraction    "UserPageVisits UserComments UserPlays UserBlocks UserDownloads UserPlusOnes UserLikes UserCheckins UserTweets"

这不是按字母顺序排列的。如果我将排序顺序替换为 desc结果完全一样。我好像不明白怎么 group by , order by可能还有 bind相互影响。

Answer 1

附加 select需要子查询来推送组内的订单:

prefix schema:  <http://schema.org/>
prefix rdfs:    <http://www.w3.org/2000/01/rdf-schema#>

select    ?child  (group_concat (?string) as ?strings) 

where {
    select * 
    {
     ?child  rdfs:subClassOf schema:Event .
     ?grandchild rdfs:subClassOf ?child .
     bind (strafter(str(?grandchild), "http://schema.org/") as ?string)
    } order by asc(?string)
}   group by ?child  
limit 20