---
acl_categories:
- '@read'
- '@set'
- '@slow'
arguments:
- display_text: key
  key_spec_index: 0
  multiple: true
  name: key
  type: key
arity: -2
categories:
- docs
- develop
- stack
- oss
- rs
- rc
- oss
- kubernetes
- clients
command_flags:
- readonly
complexity: O(N) where N is the total number of elements in all given sets.
description: Returns the union of multiple sets.
group: set
hidden: false
hints:
- nondeterministic_output_order
key_specs:
- RO: true
  access: true
  begin_search:
    spec:
      index: 1
    type: index
  find_keys:
    spec:
      keystep: 1
      lastkey: -1
      limit: 0
    type: range
linkTitle: SUNION
railroad_diagram: /images/railroad/sunion.svg
since: 1.0.0
summary: Returns the union of multiple sets.
syntax_fmt: SUNION key [key ...]
title: SUNION
---
> [!NOTE]
> This command's behavior varies in clustered Redis environments. See the [multi-key operations](/content/develop/using-commands/multi-key-operations.md) page for more information.


Returns the members of the set resulting from the union of all the given sets.

For example:

```
key1 = {a,b,c,d}
key2 = {c}
key3 = {a,c,e}
SUNION key1 key2 key3 = {a,b,c,d,e}
```

Keys that do not exist are considered to be empty sets.

## Required arguments

<details open><summary><code>key [key ...]</code></summary>

One or more set keys to union.

</details>

## Examples

{{% redis-cli %}}
redis> SADD key1 "a"
(integer) 1
redis> SADD key1 "b"
(integer) 1
redis> SADD key1 "c"
(integer) 1
redis> SADD key2 "c"
(integer) 1
redis> SADD key2 "d"
(integer) 1
redis> SADD key2 "e"
(integer) 1
redis> SUNION key1 key2
1) "a"
2) "c"
3) "d"
4) "e"
5) "b"
{{% /redis-cli %}}

## Redis Software and Redis Cloud compatibility

| Redis<br />Software | Redis<br />Cloud | <span style="min-width: 9em; display: table-cell">Notes</span> |
|:----------------------|:-----------------|:------|
| <span title="Supported">&#x2705; Standard</span><br /><span title="Supported"><nobr>&#x2705; Active-Active</nobr></span> | <span title="Supported">&#x2705; Standard</span><br /><span title="Supported"><nobr>&#x2705; Active-Active</nobr></span> |  |

## Return information

{{< multitabs id="sunion-return-info" 
    tab1="RESP2" 
    tab2="RESP3" >}}

[Array reply](../../develop/reference/protocol-spec#arrays): a list with members of the resulting set.

-tab-sep-

[Set reply](../../develop/reference/protocol-spec#sets): a set with the members of the resulting set.

{{< /multitabs >}}

## See also

[`SUNIONCARD`](/content/commands/sunioncard.md) | [`SUNIONSTORE`](/content/commands/sunionstore.md)