Returns if member is a member of the set stored at key.
返回值
Integer reply, specifically:
1if the element is a member of the set.0if the element is not a member of the set, or ifkeydoes not exist.
例子
redis>
SADD myset "one"
(integer) 1redis> SISMEMBER myset "one"
(integer) 1redis> SISMEMBER myset "two"
(integer) 0