SPARQL BIND(COUNT(...) AS ...) not working [duplicate] - sparql

Question

This question already has an answer here:
Sparql BIND result of count WITH A VARIABLE
(1 answer)
Closed 6 years ago.
I'm trying to assign a count to a variable for later use in the query (SPARQL).
I can't even get the following to work:
SELECT ?resultsCount
WHERE{
?subject ?predicate ?object.
BIND(COUNT(?object) AS ?resultsCount)
}
There is something wrong with my syntax or semantics here, as I simply get an empty result repeated ?resultsCount many times, instead of simply e.g. 86 (number of results).
However, I get the number of results (e.g. 86) when I do the following:
SELECT (COUNT(?object) AS ?resultsCount)
WHERE{
?subject ?predicate ?object
}
Is there any way to get BIND to work with COUNT like in the first example? If not, is there a different correct way to get the same sort of functionality?
I'm using Blazegraph 2.1.2. Could it be a bug with that?

Answer 1

count is an aggregate function. To use count, you need to use group by in your query, and use count in the projection. Count will count the number of results within each group. You can also use distinct with count, so you could do something like the following to get the number of distinct objects for each subject:
select ?subject (count(?object) as ?numObjects) {
?subject ?predicate ?object
}
group by ?subject
If you're just trying to count the number of matches, then you can use count without a group by (which gives you a single, implicit, group):
select (count(*) as ?numResults) {
?subject ?predicate ?object
}