# Using virtual graphs tutorial - returns zero rows back

**URL:** <https://community.stardog.com/t/using-virtual-graphs-tutorial-returns-zero-rows-back/1629>\
**Category:** Support\
**Created:** [May 1, 2019, 7:35pm UTC](https://community.stardog.com/t/using-virtual-graphs-tutorial-returns-zero-rows-back/1629 "2019-05-01T19:35:40Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![R3000](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.stardog.com/r3000/32/358_2.png) [@R3000](https://community.stardog.com/u/R3000)\
**Post date:** [May 1, 2019, 7:35pm UTC](https://community.stardog.com/t/using-virtual-graphs-tutorial-returns-zero-rows-back/1629/1 "2019-05-01T19:35:40Z")

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All worked fine with this tutorial [https://www.stardog.com/tutorials/using-virtual-graphs/](https://www.stardog.com/tutorials/using-virtual-graphs/) until executing the query below - returned zero rows.

- Do you know why?

BTW - I see the virtual graph in studio.

```
SELECT ?member ?name {
   GRAPH <virtual://music> {
      ?band a :Band ;
            :name "The Beatles" ;
            :member ?member .
      ?member :name ?name .
   }
}

```

---

<div class="post-metadata">

**Author:** ![stephen](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.stardog.com/stephen/32/27_2.png) [@stephen](https://community.stardog.com/u/stephen)\
**Post date:** [May 1, 2019, 7:46pm UTC](https://community.stardog.com/t/using-virtual-graphs-tutorial-returns-zero-rows-back/1629/2 "2019-05-01T19:46:53Z")

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Make sure that your prefixes match up between the triples that are mapped and the triples that you are querying. `:Band` can resolve to many IRIs depending on how the default prefix is defined. Check your mapping for a prefix declaration and make sure that your query is using the same one.

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<div class="post-metadata">

**Author:** ![system](https://canada1.discourse-cdn.com/flex030/uploads/stardog/original/2X/e/ed66b48a616f505106a4acde3c9cee7e6da9bc67.svg) [@system](https://community.stardog.com/u/system)\
**Post date:** [May 15, 2019, 7:46pm UTC](https://community.stardog.com/t/using-virtual-graphs-tutorial-returns-zero-rows-back/1629/3 "2019-05-15T19:46:57Z")

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