🌙 Set类型
redis Set类型和JS中的Set对象类似，存储的数值不能重复。
set特征：
- 无序
- 元素不可重复
- 查找快
- 支持交集、并集、差集等功能
Set类型常见命令： String的常见命令有：
- SADD key member ... ：向set中添加一个或多个元素
- SREM key member ... : 移除set中的指定元素
- SCARD key： 返回set中元素的个数
- SISMEMBER key member：判断一个元素是否存在于set中
- SMEMBERS：获取set中的所有元素
- SINTER key1 key2 ... ：求key1与key2的交集
- SDIFF key1 key2 ... ：求key1与key2的差集
- SUNION key1 key2 ..：求key1和key2的并集
127.0.0.1:6379> help @SET
SADD key member [member ...]
summary: Add one or more members to a set
since: 1.0.0
SCARD key
summary: Get the number of members in a set
since: 1.0.0
SDIFF key [key ...]
summary: Subtract multiple sets
since: 1.0.0
SDIFFSTORE destination key [key ...]
summary: Subtract multiple sets and store the resulting set in a key
since: 1.0.0
SINTER key [key ...]
summary: Intersect multiple sets
since: 1.0.0
SINTERSTORE destination key [key ...]
summary: Intersect multiple sets and store the resulting set in a key
since: 1.0.0
SISMEMBER key member
summary: Determine if a given value is a member of a set
since: 1.0.0
SMEMBERS key
summary: Get all the members in a set
since: 1.0.0
SMOVE source destination member
summary: Move a member from one set to another
since: 1.0.0
SPOP key [count]
summary: Remove and return one or multiple random members from a set
since: 1.0.0
SRANDMEMBER key [count]
summary: Get one or multiple random members from a set
since: 1.0.0
SREM key member [member ...]
summary: Remove one or more members from a set
since: 1.0.0
SSCAN key cursor [MATCH pattern] [COUNT count]
summary: Incrementally iterate Set elements
since: 2.8.0
SUNION key [key ...]
summary: Add multiple sets
since: 1.0.0
SUNIONSTORE destination key [key ...]
summary: Add multiple sets and store the resulting set in a key
since: 1.0.0
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🌙 练习
#将下列数据用Redis的Set集合来存储：
#张三的好友有：李四、王五、赵六
#李四的好友有：王五、麻子、二狗
SADD zs ls ww zl
SADD ls ww mz eg
#利用Set的命令实现下列功能：
#计算张三的好友有几人
SCARD zs
# 计算张三和李四有哪些共同好友
SINTER zs ls
# 查询哪些人是张三的好友却不是李四的好友
SDIFF zs ls
# 查询张三和李四的好友总共有哪些人
SUNION zs ls
# 判断李四是否是张三的好友
SISMEMBER zs ls
# 判断张三是否是李四的好友
SISMEMBER ls zs
# 将李四从张三的好友列表中移除
SREM zs ls
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