With a traditional SQL based database a HAVING clause will restrict aggregated values. For example
select zipcode, count(*) as population
from Person
group by zipcode
having population>100000;
will return all zipcodes which have more than 100k residents.
To achieve the same in Cypher use the following
match (n:Person)
with n.zipcode as zip, count(*) as population
where population>100000
return zip,population