Redis命令-有序集合-zcount

原文

http://redis.io/commands/zcount

简介

Count the members in a sorted set with scores within the given values.

计算有序集合中分数在指定值范围内的元素的数量。

语法

ZCOUNT key min max

版本

Available since 2.0.0.

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自2.0.0版本可用。

时间复杂度

Time complexity: O(log(N)) with N being the number of elements in the sorted set.

O(log(N))：N是有序集合中元素的数量。

描述

Returns the number of elements in the sorted set at key with a score between min and max.

返回有序集合中分数在min和max之间的元素的数量。

The min and max arguments have the same semantic as described for ZRANGEBYSCORE.

参数min和max与ZRANGEBYSCORE命令具有相同的语义。

Note: the command has a complexity of just O(log(N)) because it uses elements ranks (see ZRANK) to get an idea of the range. Because of this there is no need to do a work proportional to the size of the range.

返回值

Integer reply: the number of elements in the specified score range.

整数：指定分数范围内元素的数量。

例子

redis>  ZADD myzset 1 "one"
(integer) 1
redis>  ZADD myzset 2 "two"
(integer) 1
redis>  ZADD myzset 3 "three"
(integer) 1
redis>  ZCOUNT myzset -inf +inf
(integer) 3
redis>  ZCOUNT myzset (1 3
(integer) 2
redis>