🌙 SortedSet类型
Redis的SortedSet(Zset)是一个可排序的set集合，与Java中的TreeSet有些类似，但底层数据结构却差别很大。SortedSet中的每一个元素都带有一个score属性，可以基于score属性对元素排序，底层的实现是一个跳表（SkipList）加 hash表
SortedSet具备下列特性：
- 可排序
- 元素不重复
- 查询速度快
因为SortedSet的可排序特性，经常被用来实现排行榜这样的功能。
SortedSet的常见命令有：
- ZADD key score member：添加一个或多个元素到sorted set ，如果已经存在则更新其score值
- ZREM key member：删除sorted set中的一个指定元素
- ZSCORE key member : 获取sorted set中的指定元素的score值
- ZRANK key member：获取sorted set 中的指定元素的排名
- ZCARD key：获取sorted set中的元素个数
- ZCOUNT key min max：统计score值在给定范围内的所有元素的个数
- ZINCRBY key increment member：让sorted set中的指定元素自增，步长为指定的increment值
- ZRANGE key min max：按照score排序后，获取指定排名范围内的元素
- ZRANGEBYSCORE key min max：按照score排序后，获取指定score范围内的元素
- ZDIFF、ZINTER、ZUNION：求差集、交集、并集
注意：所有的排名默认都是升序，如果要降序则在命令的Z后面添加REV即可
查看SortedSet命令：
ZCARD key
summary: Get the number of members in a sorted set
since: 1.2.0
ZCOUNT key min max
summary: Count the members in a sorted set with scores within the given values
since: 2.0.0
ZINCRBY key increment member
summary: Increment the score of a member in a sorted set
since: 1.2.0
ZINTERSTORE destination numkeys key [key ...] [WEIGHTS weight] [AGGREGATE SUM|MIN|MAX]
summary: Intersect multiple sorted sets and store the resulting sorted set in a new key
since: 2.0.0
ZLEXCOUNT key min max
summary: Count the number of members in a sorted set between a given lexicographical range
since: 2.8.9
ZPOPMAX key [count]
summary: Remove and return members with the highest scores in a sorted set
since: 5.0.0
ZPOPMIN key [count]
summary: Remove and return members with the lowest scores in a sorted set
since: 5.0.0
ZRANGE key start stop [WITHSCORES]
summary: Return a range of members in a sorted set, by index
since: 1.2.0
ZRANGEBYLEX key min max [LIMIT offset count]
summary: Return a range of members in a sorted set, by lexicographical range
since: 2.8.9
ZRANGEBYSCORE key min max [WITHSCORES] [LIMIT offset count]
summary: Return a range of members in a sorted set, by score
since: 1.0.5
ZRANK key member
summary: Determine the index of a member in a sorted set
since: 2.0.0
ZREM key member [member ...]
summary: Remove one or more members from a sorted set
since: 1.2.0
ZREMRANGEBYLEX key min max
summary: Remove all members in a sorted set between the given lexicographical range
since: 2.8.9
ZREMRANGEBYRANK key start stop
summary: Remove all members in a sorted set within the given indexes
since: 2.0.0
ZREMRANGEBYSCORE key min max
summary: Remove all members in a sorted set within the given scores
since: 1.2.0
ZREVRANGE key start stop [WITHSCORES]
summary: Return a range of members in a sorted set, by index, with scores ordered from high to low
since: 1.2.0
ZREVRANGEBYLEX key max min [LIMIT offset count]
summary: Return a range of members in a sorted set, by lexicographical range, ordered from higher to lower strings.
since: 2.8.9
ZREVRANGEBYSCORE key max min [WITHSCORES] [LIMIT offset count]
summary: Return a range of members in a sorted set, by score, with scores ordered from high to low
since: 2.2.0
ZREVRANK key member
summary: Determine the index of a member in a sorted set, with scores ordered from high to low
since: 2.0.0
ZSCAN key cursor [MATCH pattern] [COUNT count]
summary: Incrementally iterate sorted sets elements and associated scores
since: 2.8.0
ZSCORE key member
summary: Get the score associated with the given member in a sorted set
since: 1.2.0
ZUNIONSTORE destination numkeys key [key ...] [WEIGHTS weight] [AGGREGATE SUM|MIN|MAX]
summary: Add multiple sorted sets and store the resulting sorted set in a new key
since: 2.0.0
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🌙 练习
# 将班级的下列学生得分存入Redis的SortedSet中：
# Jack 85, Lucy 89, Rose 82, Tom 95, Jerry 78, Amy 92, Miles 76
ZADD test:class 85 Jack 89 Lucky 82 Rose 95 Tom 78 Jerry 92 Amy 76 Miles
# 并实现下列功能：
# 删除Tom同学
ZREM test:class Tom
# 获取Amy同学的分数
ZSCORE test:class Amy
# 获取Rose同学的排名
ZRANK test:class Rose
# 查询80分以下有几个学生
ZCOUNT test:class 0 80
# 给Amy同学加2分
ZINCRBY test:class 2 Amy
# 查出成绩前3名的同学
ZREVRANGE test:class 0 2
1) "Amy"
2) "Lucky"
3) "Jack"
# 查出成绩80分以下的所有同学
ZRANGEBYSCORE test:class 0 80
1) "Miles"
2) "Jerry"
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