Redis sets redisコレクション

## SADD -- add item into set
    SADD myset "James"
    # if success, return 1, else return 0

## SMEMBERS -- check members in set
    SMEMBERS myset

## SREM -- delete members from set
    SREM myset "Harry"
    # if delete, return 1, else return 0, e.g. delete an un-exist member

## SPOP -- return and delete one key by random in set
    SPOP myset

## SDIFF --        key    key   
    SDIFF set1 set2
    # return member only in set1 and not in set2

## SDIFFSTORE --        key    key   ,           key
    SDIFFSTORE result-set set1 set2
    SMEMBERS result-set

## SINTER --        key   
    SINTER set1 set2 [set3 ... setN]

## SINTERSTORE --           set
    SINTERSTORE result-set set1 set2 [set3 ... setN]

## SUNION --   
    SUNION set1 set2 [set3 ... setN]

## SUNIONSTORE --           set
    SUNIONSTORE result-set set1 set2 [set3 ... setN]

## SMOVE --     key   set   member         set 
    SMOVE first-set result-set member-name
        127.0.0.1:6379[8]> SMEMBERS t_num2
        1) "five"
        2) "three"
        3) "one"
        127.0.0.1:6379[8]> SMOVE t_num2 t_num4 five
        (integer) 1
        127.0.0.1:6379[8]> SMEMBERS t_num2
        1) "three"
        2) "one"
        127.0.0.1:6379[8]> SMEMBERS t_num4
        1) "five"
## SCARD -- return number of the set
    SCARD myset

## SINMEMBER -- test if member is in set
    SINMEMBER myset member-name

## SRANDMEMBER --        key set     ，       
    SRANDMEMBER myset