ZCARD
Syntax
1. ZCARD key
Time complexity: O(1)
Returns the sorted set cardinality (number of elements) of the sorted set stored at key.
Return
Integer reply: the cardinality (number of elements) of the sorted set, or 0 if key does not exist.
Examples
1. dragonfly> ZADD myzset 1 "one"
2. (integer) 1
3. dragonfly> ZADD myzset 2 "two"
4. (integer) 1
5. dragonfly> ZCARD myzset
6. (integer) 2
