返回有序集key中，score值在min和max之间(默认包括score值等于min或max)的成员。 关于参数min和max的详细使用方法，请参考ZRANGEBYSCORE命令。

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.

返回值

integer-reply: 指定分数范围的元素个数。

例子

redis> ZADD myzset 1 "one"
(integer) 1
redis> ZADD myzset 2 "two"
(integer) 1
redis> ZADD myzset 3 "three"
(integer) 1
redis> ZCOUNT myzset -inf +inf
(integer) 3
redis> ZCOUNT myzset (1 3
(integer) 2
redis>