Error on query against multiple virtual graphs

Support Bug
1

Hello,
I am trying to run a SPARQL query against multiple virtual graphs.
I am able to get the expected results if I use the union operator, as in the following:

SELECT *
WHERE {
{
GRAPH virtual://aiw {
?a ?b ?c.
}
}
UNION
{
GRAPH virtual://tw_mockdb2 {
?a ?b ?c.
}
}
}
However, if I attempt to run the query without the union, using the following format, no results are returned (nor is there an error):
SELECT *
FROM virtual://tw_mockdb2
FROM virtual://aiw
WHERE
{
GRAPH ?g {
?a ?b ?c.
}
}

I came across an earlier, similar topic (Combining virtual graphs and the other graphs) and the response indicates that the issue would be corrected in a 2019 release however it doesn't seem to be working.

2

This is working as expected. If you change your line from 'FROM' to 'FROM NAMED' it should work.

To help understand the disctinction, please refer to slide 54-56 of our Getting Started with RDF and SPARQL from our Stardog University series.

3

Hello,
Thank you for the quick response. I also tried using "FROM NAMED" in the query, (as below) however no results are returned.

SELECT *
FROM NAMED virtual://tw_mockdb2
FROM NAMED virtual://aiw
WHERE
{
GRAPH ?g {
?a ?b ?c.
}
}

4

Hi Megan,

Currently it is required to enable the "Virtual Transparency" database option to use virtual graphs in the dataset (FROM and FROM NAMED).

Jess

5

Hi Jess,
Thank you! Found the option and it works perfectly!

Megan