> ## Documentation Index
> Fetch the complete documentation index at: https://upstash.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# ZUNIONSTORE

> Store sorted set union.

Use `ZUNIONSTORE` to compute the union of sorted sets and store it in another key.

Members present in several inputs are scored by the sum of their scores by default, or by `MIN` or `MAX` when `AGGREGATE` is given, with `WEIGHTS` scaling each input first. The destination is overwritten if it exists and deleted when the union is empty, and the reply is the number of members stored.

Merging per-day or per-source rankings into a combined one, weighting them as you go, is the typical use: the destination is an ordinary sorted set that can then be paged with [`ZRANGE`](/docs/redis/commands/sorted-set/zrange).

## Syntax

```redis theme={"system"}
ZUNIONSTORE <destination> <numkeys> <key> [<key> ...]
  [WEIGHTS <weight> [<weight> ...]]
  [AGGREGATE SUM | MIN | MAX]
```

## Arguments

| Argument                        | Required | Repeatable | Description                                                                      |
| ------------------------------- | -------- | ---------- | -------------------------------------------------------------------------------- |
| `<destination>`                 | Yes      | No         | Redis key used as destination.                                                   |
| `<numkeys>`                     | Yes      | No         | Number of key arguments that follow.                                             |
| `<key>`                         | Yes      | Yes        | Redis key targeted by the command.                                               |
| `WEIGHTS <weight>`              | No       | Yes        | Multiplier applied to each input key's scores, in the order the keys were given. |
| `(AGGREGATE SUM \| MIN \| MAX)` | No       | No         | Under `AGGREGATE`, choose one form: `SUM`; `MIN`; `MAX`.                         |

## Important points

* `numkeys` must equal the number of key arguments that immediately follow it.

## Response

The reply reports the result of the operation. Error replies have the same shape in RESP2 and RESP3 and are surfaced as exceptions by the SDKs below.

| Protocol | Reply   |
| -------- | ------- |
| RESP2    | Integer |
| RESP3    | Integer |

<Note>
  Client libraries often decode bulk strings, maps, sets, and numeric strings into language-native values. The table describes the Redis wire reply.
</Note>

## Examples

TCP examples use the TLS `REDIS_URL` from the Upstash console. REST examples use `UPSTASH_REDIS_REST_URL` and `UPSTASH_REDIS_REST_TOKEN`.

<AccordionGroup>
  <Accordion title="Redis CLI" icon="terminal">
    ```bash theme={"system"}
    ZUNIONSTORE destination-key 1 my-key
    ```
  </Accordion>

  <Accordion title="@upstash/redis" icon="node-js" iconType="brands">
    ```ts theme={"system"}
    import { Redis } from "@upstash/redis";

    const redis = Redis.fromEnv();

    await redis.zadd(
        "key1",
        { score: 1, member: "member1" },
    )
    await redis.zadd(
        "key2",
        { score: 1, member: "member1" },
        { score: 2, member: "member2" },
    )

    const res = await redis.zunionstore("destination", 2, ["key1", "key2"]);
    console.log(res) // 2
    ```
  </Accordion>

  <Accordion title="upstash_redis" icon="python" iconType="brands">
    ```python theme={"system"}
    from upstash_redis import Redis

    redis = Redis.from_env()
    result = redis.zunionstore("destination-key", ["my-key"])
    print(result)
    ```
  </Accordion>

  <Accordion title="ioredis" icon="node-js" iconType="brands">
    ```ts theme={"system"}
    import Redis from "ioredis";

    const redis = new Redis(process.env.REDIS_URL!);
    const result = await redis.zunionstore("destination-key", "1", "my-key");
    console.log(result);
    ```
  </Accordion>

  <Accordion title="node-redis" icon="node-js" iconType="brands">
    ```ts theme={"system"}
    import { createClient } from "redis";

    const client = await createClient({ url: process.env.REDIS_URL })
      .on("error", console.error)
      .connect();
    const result = await client.zUnionStore("destination-key", "my-key");
    console.log(result);
    ```
  </Accordion>

  <Accordion title="redis-py" icon="python" iconType="brands">
    ```python theme={"system"}
    import os
    import redis

    client = redis.from_url(os.environ["REDIS_URL"])
    result = client.zunionstore("destination-key", ["my-key"])
    print(result)
    ```
  </Accordion>

  <Accordion title="go-redis" icon="golang" iconType="brands">
    ```go theme={"system"}
    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)
        result, err := client.ZUnionStore(context.Background(), "destination-key", &redis.ZStore{Keys: []string{"my-key"}}).Result()
        if err != nil {
            panic(err)
        }
        fmt.Println(result)
    }
    ```
  </Accordion>

  <Accordion title="jedis" icon="java" iconType="brands">
    ```java theme={"system"}
    import java.net.URI;

    import redis.clients.jedis.Jedis;

    try (Jedis jedis = new Jedis(new URI(System.getenv("REDIS_URL")))) {
      Object result = jedis.zunionstore("destination-key", "my-key");
      System.out.println(result);
    }
    ```
  </Accordion>

  <Accordion title="redis-rs" icon="rust" iconType="brands">
    ```rust theme={"system"}
    use redis::TypedCommands;

    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 result = connection.zunionstore("destination-key", &["my-key"])?;
        println!("{result:?}");
        Ok(())
    }
    ```
  </Accordion>
</AccordionGroup>


## Related topics

- [ZUNIONSTORE](/docs/redis/sdks/ts/commands/zset/zunionstore.md)
- [ZUNION](/docs/redis/commands/sorted-set/zunion.md)
- [Overview](/docs/redis/sdks/py/commands/overview.md)