On 24/11/15 13:14, Wetz Peter wrote:
Thanks Rob, this also does the job.
What are advantages of this approach compared to using BIND() ? Performance?
Thanks again and best,
Peter
Not much difference. They are the same operation with same rules as to
what you can and can't do. They happen at slightly different places in
execution but you can get the same effects with (more) subqueries and
use of {}
Using BIND at the end of the WHERE clause and using AS in SELECT only
differs by availability of other variables:
SELECT ?s (AVG(?single) as ?agg) (?agg+10 AS ?var) {
} GROUP BY ?s
==>
SELECT * {
{SELECT ?s (AVG(?single) as ?agg) { }
GROUP BY ?s
}
BIND(?agg+10 AS ?var)
}
For fixed expressions, there is also VALUES -- inline data in the query.
Andy
-----Ursprüngliche Nachricht-----
Von: Rob Vesse [mailto:[email protected]]
Gesendet: Dienstag, 24. November 2015 12:02
An: [email protected]
Betreff: Re: BIND in CONSTRUCT query with sub-SELECT (SPARQL)
Instead of BIND you can simply use a project expression, this is essentially
the same as you would do for a BIND but placed on the SELECT line with
variables and aggregates e.g.
PREFIXES
CONSTRUCT { ?s rdfs:label ?var . }
WHERE {
SELECT ?s (AVG(?single) as ?agg) (IRI(expr) AS ?var)
WHERE {
...
}
GROUP BY ?s ...
}
Where expr is some expression that generates your desired constant
Rob
On 24/11/2015 10:24, "Wetz Peter" <[email protected]> wrote:
Related to the answer of a previous question of mine (see [1]) I have a
new question: I currently have a CONSTRUCT query with a nested SELECT
which makes use of aggregates. What I now want to do is to construct
new URIs in the CONSTRUCT statement.
What I want to do is basically similar as can be seen in [2]. There I
see that BIND is used in the WHERE class to construct new URIs which
are then used in the CONSTRUCT clause. Unfortunately this approach does
not work for my case (nested SELECT which resides in the CONSTRUCT's
WHERE clause). The difference is, that in this example no nested SELECT
is present.
My current query looks like this (simplified):
PREFIXES
CONSTRUCT { ?s rdfs:label ?var . }
WHERE {
SELECT ?s (AVG(?single) as ?agg)
WHERE {
...
}
GROUP BY ?s ...
}
The question is: Where to place a BIND statement which is used to bind
values to variables, which are then used in the CONSTRUCT statement (e.g.
?var)?
Thanks for your help.
Best,
Peter
[1]
https://mail-archives.apache.org/mod_mbox/jena-
users/201511.mbox/%3C194
403 [email protected]%3E
[2]
http://mail-archives.apache.org/mod_mbox/jena-
users/201111.mbox/%3C4ED6
672
[email protected]%3E
