ZCARD
ZCARD key
Returns the sorted set cardinality (number of elements) of the sorted set stored at key.
Return value
Integer reply: the cardinality (number of elements) of the sorted set, or 0 if key does not exist.
Examples
 redis>  ZADD myzset 1 "one" 
  (integer) 1 redis>  ZADD myzset 2 "two" (integer) 1 redis>  ZCARD myzset (integer) 2
    © 2009–2020 Salvatore Sanfilippo
Licensed under the Creative Commons Attribution-ShareAlike License 4.0.
    https://redis.io/commands/zcard