一、特点
Redis 有序集合和集合一样也是 string 类型元素的集合,且不允许重复的成员。
不同的是每个元素都会关联一个 double 类型的分数。redis 正是通过分数来为集合中的成员进行从小到大的排序。
有序集合的成员是唯一的,但分数(score)却可以重复。
集合是通过哈希表实现的，所以添加，删除，查找的复杂度都是 O(1)。 集合中最大的成员数为 232 - 1 (4294967295, 每个集合可存储40多亿个成员)。
二、操作
1）BZPOPMAX key [key ...] timeout 移除并返回一个或多个排序集合中得分最高的成员，或阻塞，直到有一个可用
summary: Remove and return the member with the highest score from one or more sorted sets, or block until one is available
since: 5.0.0
2）BZPOPMIN key [key ...] timeout 移除并返回一个或多个排序集合中得分最低的成员，或阻塞，直到有一个可用
summary: Remove and return the member with the lowest score from one or more sorted sets,or block until one is available
since: 5.0.0
3）ZADD key [NX|XX] [GT|LT] [CH] [INCR] score member [score member ...] 向已排序的集合添加一个或多个成员，如果集合已经存在，则更新其分数
summary: Add one or more members to a sorted set, or update its score if it already exists
since: 1.2.0
4）ZCARD key 得到一个排序集合的成员数
summary: Get the number of members in a sorted set
since: 1.2.0
5）ZCOUNT key min max 对分数在给定值内的排序集合中的成员进行计数
summary: Count the members in a sorted set with scores within the given values
since: 2.0.0
6）ZDIFF numkeys key [key ...] [WITHSCORES] 求差集
summary: Subtract multiple sorted sets
since: 6.2.0
7）ZDIFFSTORE destination numkeys key [key ...] 求差集并将结果放入另一个集合中
summary: Subtract multiple sorted sets and store the resulting sorted set in a new key
since: 6.2.0
8）ZINCRBY key increment member 递增已排序集合中成员的分数
summary: Increment the score of a member in a sorted set
since: 1.2.0
9）ZINTER numkeys key [key ...] [WEIGHTS weight] [AGGREGATE SUM|MIN|MAX] [WITHSCORES] 求交集
summary: Intersect multiple sorted sets
since: 6.2.0
10）ZINTERSTORE destination numkeys key [key ...] [WEIGHTS weight] [AGGREGATE SUM|MIN|MAX] 与多个排序集相交，并将结果排序集存储在一个新键中
summary: Intersect multiple sorted sets and store the resulting sorted set in a new key
since: 2.0.0
11）ZLEXCOUNT key min max 计算在给定的字典范围之间的排序集合中的成员数
summary: Count the number of members in a sorted set between a given lexicographical range
since: 2.8.9
12）ZMSCORE key member [member ...] 获取一个排序集合中与给定成员相关联的分数
summary: Get the score associated with the given members in a sorted set
since: 6.2.0
13）ZPOPMAX key [count] 移除并返回排序集合中得分最高的成员
summary: Remove and return members with the highest scores in a sorted set
since: 5.0.0
14）ZPOPMIN key [count] 移除并返回排序集合中得分最低的成员
summary: Remove and return members with the lowest scores in a sorted set
since: 5.0.0
15）ZRANDMEMBER key [count [WITHSCORES]] 从一个排序集合中获取一个或多个随机元素
summary: Get one or multiple random elements from a sorted set
since: 6.2.0
16）ZRANGE key min max [BYSCORE|BYLEX] [REV] [LIMIT offset count] [WITHSCORES] 返回已排序集合中的成员范围
summary: Return a range of members in a sorted set
since: 1.2.0
17）ZRANGEBYLEX key min max [LIMIT offset count] 按字典序范围返回已排序集合中的成员范围
summary: Return a range of members in a sorted set, by lexicographical range
since: 2.8.9
18）ZRANGEBYSCORE key min max [WITHSCORES] [LIMIT offset count] 按分数返回已排序集合中的成员范围
summary: Return a range of members in a sorted set, by score
since: 1.0.5
19）ZRANGESTORE dst src min max [BYSCORE|BYLEX] [REV] [LIMIT offset count] 将排序集的成员范围存储到另一个键中
summary: Store a range of members from sorted set into another key
since: 6.2.0
20）ZRANK key member 确定已排序集合中成员的索引
summary: Determine the index of a member in a sorted set
since: 2.0.0
21）ZREM key member [member ...] 从已排序集合中移除一个或多个成员
summary: Remove one or more members from a sorted set
since: 1.2.0
22）ZREMRANGEBYLEX key min max 移除已排序集合中给定词序范围之间的所有成员
summary: Remove all members in a sorted set between the given lexicographical range
since: 2.8.9
23）ZREMRANGEBYRANK key start stop 移除给定索引内已排序集合中的所有成员
summary: Remove all members in a sorted set within the given indexes
since: 2.0.0
24）ZREMRANGEBYSCORE key min max 移除给定分数内已排序集合中的所有成员
summary: Remove all members in a sorted set within the given scores
since: 1.2.0
25）ZREVRANGE key start stop [WITHSCORES] 按索引返回已排序集合中的成员范围，其分数从高到低排序
summary: Return a range of members in a sorted set, by index, with scores ordered from high to low
since: 1.2.0
26）ZREVRANGEBYLEX key max min [LIMIT offset count] 返回已排序集合中的成员范围(按字典序范围从高到低排序
summary: Return a range of members in a sorted set, by lexicographical range, ordered from higher to lower strings.
since: 2.8.9
27）ZREVRANGEBYSCORE key max min [WITHSCORES] [LIMIT offset count] 返回按分数排序的已排序集合中的成员范围，分数从高到低排序
summary: Return a range of members in a sorted set, by score, with scores ordered from high to low
28）since: 2.2.0
29）ZREVRANK key member 确定已排序集合中成员的索引，其分数从高到低排序
summary: Determine the index of a member in a sorted set, with scores ordered from high to low
since: 2.0.0
30）ZSCAN key cursor [MATCH pattern] [COUNT count] 递增迭代排序的集合元素和相关的分数
summary: Incrementally iterate sorted sets elements and associated scores
since: 2.8.0
31）ZSCORE key member 获取与已排序集合中给定成员相关联的分数
summary: Get the score associated with the given member in a sorted set
since: 1.2.0
32）ZUNION numkeys key [key ...] [WEIGHTS weight] [AGGREGATE SUM|MIN|MAX] [WITHSCORES] 添加多个排序集
summary: Add multiple sorted sets
since: 6.2.0
33）ZUNIONSTORE destination numkeys key [key ...] [WEIGHTS weight] [AGGREGATE SUM|MIN|MAX] 添加多个排序集并将结果存储在一个新键中
summary: Add multiple sorted sets and store the resulting sorted set in a new key
since: 2.0.0
三、应用场景
1、 排行榜：有序集合经典使用场景。例如视频网站需要对用户上传的视频做排行榜，榜单维护可能是多方面：按照时间、按照播放量、按照获得的赞数等。
2、用Sorted Sets来做带权重的队列，比如普通消息的score为1，重要消息的score为2，然后工作线程可以选择按score的倒序来获取工作任务。让重要的任务优先执行。
