SCARD
Syntax
        SCARD key
- Available since:
 - 1.0.0
 - Time complexity:
 - O(1)
 - ACL categories:
 - 
              
                
@read,@set,@fast, 
Returns the set cardinality (number of elements) of the set stored at key.
Examples
RESP2 Reply
Integer reply: the cardinality (number of elements) of the set, or0 if the key does not exist.