redis数据类型-有序集合
ZADD:添加元素：
192.168.2.120:6379> ZADD youxu 80 a
(integer) 1
192.168.2.120:6379> ZADD youxu 81 b
(integer) 1
192.168.2.120:6379> ZADD youxu 82 c 83 d
(integer) 2
获取元素的分数：
192.168.2.120:6379> ZSCORE youxu a
"80"
192.168.2.120:6379> ZSCORE youxu b
"81"
192.168.2.120:6379> ZSCORE youxu c
"82"
192.168.2.120:6379> ZSCORE youxu d
"83"
按元素排列;
192.168.2.120:6379> ZRANGE youxu 0 3
1) "a"
2) "b"
3) "c"
4) "d"
192.168.2.120:6379> ZADD youxu 79 e
(integer) 1
192.168.2.120:6379> ZRANGE youxu 0 4
1) "e"
2) "a"
3) "b"
4) "c"
5) "d"
