# ZUNIONSTORE

> Writes the union between sets to a new key.

## Arguments 

<ParamField body="destination" type="string" required>
  The key to write the union to.
</ParamField>

<ParamField body="keys" type="integer" required>
  How many keys to compare.
</ParamField>

<ParamField body="keys" type="string | string[]" required>
  The keys to compare.
</ParamField>

<ParamField body="options">
    <ParamField body="aggregate" type="sum | min | max">
        The aggregation method.
    </ParamField>

    <ParamField body="weight" type="number">
        The weight to apply to each key.
    </ParamField>
    
    <ParamField body="weights" type="number[]">
        The weights to apply to each key.
    </ParamField>
    
</ParamField>

## Response

<ResponseField  required>
    The number of elements in the resulting set.
</ResponseField>



<RequestExample>
```ts Simple
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
```

```ts With Weights
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"],
    { weights: [2, 3] },
);
console.log(res) // 2
```


```ts Aggregate
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"],
    { aggregate: "sum" },
);
console.log(res) // 2
```
</RequestExample>