Hi all,
I'm trying to perform sparql query to find <video_id, category, score>
triples with an union
aggregating all the matching scores over a video_id.
However, the score is returned as blank. Here's how I construct the query
select ?v (sum(?s99*2+?s0) AS ?ss) where {
{ ?v <http://onescreen.com/video_freebase#/music/track> ?s99 }
union
{ ?v <http://onescreen.com/video_freebase#/music> ?s0 }
} group by ?v order by desc (?ss) limit 100
---------------------------------------------
| v | ss |
=============================================
| <http://onescreen.com/video#1732760> | |
| <http://onescreen.com/video#1732780> | |
| <http://onescreen.com/video#1732800> | |
but selecting with the specific video_id, the record does have both, but on
different columns:
select ?s0 ?s99 where {
{ <http://onescreen.com/video#1732760> <
http://onescreen.com/video_freebase#/music> ?s0 }
union
{ <http://onescreen.com/video#1732760> <
http://onescreen.com/video_freebase#/music/track> ?s99 }
}
-------------------------------------------------------------------------------------------------------------
| s0 | s99
|
=============================================================================================================
| "0.01532"^^<http://www.w3.org/2001/XMLSchema#float> |
|
| |
"0.00739"^^<http://www.w3.org/2001/XMLSchema#float> |
-------------------------------------------------------------------------------------------------------------
looks like it is caused by blank variable, either sum() or + with a blank
causes the result to be blank.
I noticed that I couldn't map the two columns into the same variable name,
as I'd like to apply different weights ?s99 and ?s0
to achieve sum(?s99*2+?s0)
so, with which function could I make a variable to be 0 when it is blank?
what is the correct way to construct this query?
Thank you.
Yuhan
