原文

http://redis.io/commands/zrank

简介

Determine the index of a member in a sorted set.

确定有序集合中成员的索引。

语法

ZRANK key member

版本

Available since 2.0.0.

自2.0.0版本可用。

时间复杂度

Time complexity: O(log(N))

描述

Returns the rank of member in the sorted set stored at key, with the scores ordered from low to high. The rank (or index) is 0-based, which means that the member with the lowest score has rank 0.

返回有序集合中成员的次序，按照分数从低到高排序。次序（或索引）是基于0的，这意味着分数最低的成员的次序为0。

Use ZREVRANK to get the rank of an element with the scores ordered from high to low.

使用ZREVRANGE获取元素的次序，按照分数由高到低排序。

返回值

If member exists in the sorted set, Integer reply: the rank of member.

If member does not exist in the sorted set or key does not exist, Bulk string reply: nil.

1）如果成员在有序集合中存在，返回成员的次序。
2）如果成员在有序集合中不存在，或者key不存在，返回nil。

例子

redis>  ZADD myzset 1 "one"
(integer) 1
redis>  ZADD myzset 2 "two"
(integer) 1
redis>  ZADD myzset 3 "three"
(integer) 1
redis>  ZRANK myzset "three"
(integer) 2
redis>  ZRANK myzset "four"
(nil)
redis>