SDIFFCARD - Upstash Documentation

Use SDIFFCARD to count the members of the first set that are not present in any of the other sets. It returns only the count; use SDIFF to retrieve the members. Keys that do not exist count as empty sets, so a missing first key returns 0. The command does not modify the source sets or store the difference. LIMIT stops counting once that many members have been found and returns the limit. For example, LIMIT 1 checks whether the difference contains any members. Omitting LIMIT or using LIMIT 0 returns the full count.

Syntax

SDIFFCARD <numkeys> <key> [<key> ...] [LIMIT <limit>]

Arguments

Argument	Required	Repeatable	Description
`<numkeys>`	Yes	No	Positive integer specifying how many key arguments follow.
`<key>`	Yes	Yes	Set key. Members of all subsequent sets are excluded from the first set.
`LIMIT <limit>`	No	No	Non-negative integer that caps the returned count; `0` means no limit.

Important points

numkeys must equal the number of key arguments that immediately follow it.
Key order matters: the command subtracts the other sets from the first set.
With one key, the command returns that set’s cardinality, capped by a positive LIMIT.

Response

The number of members in the difference, capped by LIMIT when it is positive.

Protocol	Reply
RESP2	Integer
RESP3	Integer

Examples

TCP examples use the TLS REDIS_URL from the Upstash console. Client examples query set1 and set2 from the Redis CLI example.

Redis CLI

> SADD set1 a b c
(integer) 3
> SADD set2 c d e
(integer) 3
> SDIFFCARD 2 set1 set2
(integer) 2
> SDIFFCARD 2 set1 set2 LIMIT 1
(integer) 1
> SDIFFCARD 2 set1 set2 LIMIT 0
(integer) 2

The difference contains a and b, so its cardinality is 2.

@upstash/redis

This command is not supported yet in @upstash/redis.

upstash_redis

This command is not supported yet in upstash_redis.

ioredis

import Redis from "ioredis";

const redis = new Redis(process.env.REDIS_URL!);
const result = await redis.sdiffcard(2, "set1", "set2");
console.log(result);

node-redis

import { createClient } from "redis";

const client = await createClient({ url: process.env.REDIS_URL })
  .on("error", console.error)
  .connect();
const result = await client.sDiffCard(["set1", "set2"]);
console.log(result);

redis-py

import os
import redis

client = redis.from_url(os.environ["REDIS_URL"])
result = client.sdiffcard(2, ["set1", "set2"])
print(result)

go-redis

package main

import (
    "context"
    "fmt"
    "os"

    "github.com/redis/go-redis/v9"
)

func main() {
    opts, err := redis.ParseURL(os.Getenv("REDIS_URL"))
    if err != nil {
        panic(err)
    }
    client := redis.NewClient(opts)
    defer client.Close()
    result, err := client.SDiffCard(context.Background(), nil, "set1", "set2").Result()
    if err != nil {
        panic(err)
    }
    fmt.Println(result)
}

jedis

import java.net.URI;

import redis.clients.jedis.Jedis;

try (Jedis jedis = new Jedis(new URI(System.getenv("REDIS_URL")))) {
  long result = jedis.sdiffcard("set1", "set2");
  System.out.println(result);
}

redis-rs

fn main() -> redis::RedisResult<()> {
    let url = std::env::var("REDIS_URL").expect("REDIS_URL is not set");
    let client = redis::Client::open(url)?;
    let mut connection = client.get_connection()?;

    let mut command = redis::cmd("SDIFFCARD");
    command.arg(2).arg("set1").arg("set2");
    let result: i64 = command.query(&mut connection)?;
    println!("{result:?}");
    Ok(())
}

​Syntax

​Arguments

​Important points

​Response

​Examples

Syntax

Arguments

Important points

Response

Examples