Hi Albert,
On 12-Apr-16 8:21 PM, Albert Meroño Peñuela wrote:
Hi all,
I'm trying to implement a custom aggregate function in Virtuoso.
Following the examples at [1] I've written something silly of the style
CREATE PROCEDURE DB.DBA.MyAggregate (IN X NUMERIC) {
declare m numeric;
m := m + X;
return m;
};
With the intention of accumulating all bindings of X.The obvious
problem with this procedure is that calling it from e.g. SPARQL will
result in one result per variable binding
SQL> sparql select (sql:myAggreagate(?val)) where { [] ?var ?val .};
(Many rows)
while what I'm trying to achieve is to use all bindings of ?val to
produce a resultset of exactly one row. There's seems to be an old
related question [2], but I can't seem to find related documentation
on this. Any help would be greatly appreciated!
Virtuoso supports SPARQL 1.1., so simply could be used the SUM function:
SELECT (SUM(?val) AS ?totalVAL)
WHERE {
[] ?var ?val .
}
Another variant is to use the Virtuoso sum function --
http://docs.openlinksw.com/virtuoso/xpf_sum.html
SELECT (bif:sum(?val) AS ?totalVAL)
WHERE {
[] ?var ?val .
}
If you however want to sum the values with a custom sql function
instead, you can try these ones:
-- result: -- http://docs.openlinksw.com/virtuoso/fn_result.html
-- result_names: -- http://docs.openlinksw.com/virtuoso/fn_result_names.html
-- end_result: -- http://docs.openlinksw.com/virtuoso/fn_end_result.html
Best Regards,
Rumyana Kocis
Thanks,
Albert
[1] http://docs.openlinksw.com/virtuoso/rdfsparql.html#rdfsqlfromsparql
[2]
https://www.mail-archive.com/virtuoso-users@lists.sourceforge.net/msg04826.html
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