Is there a SPARQL query to yield the total number of items (in the database)?

Question

using this SPARQL query on Wikidata Query Service

# Number of items with P31 (instance of) being Q15284 (municipality)
SELECT (COUNT(?item) AS ?item) WHERE {    
  ?item (wdt:P31) wd:Q15284 .    
}

the result has one row with the only one colum count at the moment indicatas 4248.

I would not only know the number of those items in the database that are limited by some attribute, but indeed the number of all items

SELECT (COUNT(?item) AS ?item) WHERE {    
# empty because I do not want any limitation
}

expected result should be number of all items in the database.

I attempt to read the specs and it appears that it is not even possible?

Hence the question here, is there a (hackish) way to use SPARQL to select all items, as to be able to count them?