-------------------------------------------------- Set collection ------------------------------------------------ ------
Sadd Key element [element ...] is added to the elements in the set
if the set of memory exists key
srem key element [element ...] remove the set of 0-n elements
scard key element number calculating
sismember key element determining whether the element in the collection
srandmember key count from a randomly selected set of n elements
spop key element in the collection of random pop-up, and remove elements from the collection
smembers key obtaining a collection of all elements in the set is unordered.
sinter key1 key2 [key ...] the sum of two or more set intersection
sunion key1 key2 [key ...] and set the sum of two or more sets
sdiff key1 key2 [key ...] and the difference between the sum of two or more sets of set
-------------------------------------------------- Set collection ------------------------------------------------ ------