ZCARD
SYNOPSIS
ZCARD key
This command returns the number of members in the sorted set at key. If key does not exist, 0 is returned.
If key is associated with non sorted-set data, an error is returned.
RETURN VALUE
The cardinality of the sorted set.
EXAMPLES
$ ZADD z_key 1.0 v1 2.0 v2
(integer) 2
$ ZADD z_key 3.0 v2
(integer) 0
$ ZCARD z_key
(integer) 2
$ ZCARD ts_key
(integer) 0