How to query Wikidata (SPARQL) by official website property P856?

Question

How can you search the Wikidata SPARQL query service for a record whose official website (property P856) matches a specific value?

For example, fetch all records whose official website is "https://www.google.com". This should return Q95 and Q9366, but instead the following query yields no results:

SELECT ?entity
WHERE  {
    ?entity wdt:P856 "https://www.google.com"
}

I can get it to work with a FILTER, but it's very slow:

SELECT ?entity
WHERE  {
    ?entity wdt:P856 ?url FILTER(str(?url)="https://www.google.com")
}

Using FILTER seems very inefficient. Why doesn't the first query work?

Answer 1

Look at the values you get from this query --

SELECT ?entity ?value
WHERE 
  {
    ?entity wdt:P856 ?value
  }
LIMIT 25

Note that they're all wrapped in <>, marking them as URIs. To compare a URI with a string literal, you must change the URI to a string, as you are doing in the second query.

In other words -- there are no entities with an official website of "https://www.google.com", but there are some entities with an official website of <https://www.google.com>.