redis ZCARD command

1. card

##UK[kɑ:d] US[kɑ:rd]

n.Card; Credit card; playing cards; postcard

vt. recorded on the card

Third person singular: cards Plural: cards Present participle: carding Past tense: carded Past participle: carded

redis ZCARD commandsyntax

Function: Returns the cardinality of the ordered set key.

Syntax: ZCARD key

Available versions: >= 1.2.0

Time complexity: O(1)

Return: When key exists and is an ordered set type, return the cardinality of the ordered set. When key does not exist, return 0.

redis ZCARD commandexample

redis > ZADD salary 2000 tom    # 添加一个成员
(integer) 1
redis > ZCARD salary
(integer) 1
redis > ZADD salary 5000 jack   # 再添加一个成员
(integer) 1
redis > ZCARD salary
(integer) 2
redis > EXISTS non_exists_key   # 对不存在的 key 进行 ZCARD 操作
(integer) 0
redis > ZCARD non_exists_key
(integer) 0