Returns the number of elements in the sorted set at key with a score between
min and max.
The min and max arguments have the same semantic as described for
ZRANGEBYSCORE.
Note: the command has a complexity of just O(log(N)) because it uses elements ranks (see ZRANK) to get an idea of the range. Because of this there is no need to do a work proportional to the size of the range.
@return
@integer-reply: the number of elements in the specified score range.
@examples
ZADD myzset 1 "one"
ZADD myzset 2 "two"
ZADD myzset 3 "three"
ZCOUNT myzset -inf +inf
ZCOUNT myzset (1 3