Collection types set
redis Set of unordered collection of type string, is the only member of the collection, that duplication of data collection can not appear
Collection type set - Common Commands
sadd /smembers /sismember /scard /srem /srandmember /spop
sadd
语法：sadd key member [member…]
effect:
One or more elements to a set of key member which,
Already exist in the member elements of the set will be ignored and will not join.
Return Value: the number of new elements added to the collection. It does not include the neglected element.
smembers
Syntax: smembers key
Role: Get all the members of key elements in the collection, regarded as non-existent key empty set
sismember
语法：sismember key member
Role: to determine whether the element is a member of a collection of key members
Return value: member is a set of member returns 1, else return 0
scard
Syntax: scard key
Action: Get the number of elements inside the collection
Return Value: the number of elements numbers, key in. Otherwise return 0
srem
语法：srem key member [member…]
Role: delete a collection of one or more member elements key in, there is no element is ignored.
Returns: the number of elements of digital, successfully removed, excluding overlooked element.
srandmember
Syntax: srandmember key [count]
effect:
Only key, random returns a collection element, the element is not deleted, still in the collection;
Providing a count, count the number of positive, returns the set count number of elements comprising a set element varies.
count is negative, returns a count of the absolute value of the set length, the collection element may be repeated several times.
Returns: an element; a plurality of collection elements
spop
Syntax: spop key [count]
Role: random delete an element from the collection, count is the number of elements that were removed.
Returns: deleted elements, key does not exist or empty collection returns nil