Redis Collection (SET)

Redis's set is an unordered collection of type string. A collection member is unique, which means that duplicate data cannot appear in the collection.

The collection in Redis is implemented by a hash table, so the complexity of adding, deleting, and finding is O (1).

The maximum number of members in the collection is 232-1 (4294967295, each of which can store 40多亿个 members).

Instance

2. Redis 127.0. 0.1:6379> sadd w3ckey redis
4. (integer) 1
6. Redis 127.0. 0.1:6379> sadd w3ckey mongodb
8. (integer) 1
10. Redis 127.0. 0.1:6379> sadd w3ckey mysql
12. (integer) 1
14. Redis 127.0. 0.1:6379> sadd w3ckey mysql
16. (integer) 0
18. Redis 127.0. 0.1:6379> smembers w3ckey
22. 1) "MySQL"
24. 2) "MongoDB"
26. 3) "Redis"

In the above example we insert three elements into the collection named W3ckey with the sadd command.

Redis Collection Commands

The following table lists the Redis collection basic commands:

Serial Number	Command and Description
1	Sadd key Member1 [member2] adds one or more members to the collection
2	SCard Key gets the number of members of the collection
3	Sdiff Key1 [Key2] Returns the difference set for all sets given
4	Sdiffstore destination Key1 [Key2] Returns the difference set for all sets and is stored in destination
5	SINTER Key1 [Key2] returns the intersection of all sets given
6	Sinterstore destination Key1 [Key2] returns the intersection of all sets given and stored in destination
7	Sismember Key member determines whether the member element is a member of the collection key
8	Smembers Key returns all members in the collection
9	Smove Source Destination member moves the member element from the source collection to the destination collection
10	SPOP key to remove and return a random element from the collection
11	Srandmember key [Count] returns one or more random numbers in the collection
12	Srem key Member1 [member2] removes one or more members from the collection
13	Sunion Key1 [Key2] Returns the set of all the given sets
14	Sunionstore destination Key1 [Key2] The aggregation of all given collections is stored in the destination collection
15	Sscan key cursor [MATCH pattern] [count count] elements in the iteration collection

Redis Collection (SET)