> ## Documentation Index
> Fetch the complete documentation index at: https://cache-pot.thatdevguy.in/llms.txt
> Use this file to discover all available pages before exploring further.

# Set commands in Cache-Pot: SADD, SMEMBERS, SISMEMBER

> Reference for Cache-Pot set commands: SADD, SREM, SMEMBERS, SISMEMBER, SCARD. Sets are unordered collections of unique string members.

A set is an unordered collection of unique string members. Unlike lists, a set will never hold two identical values — attempting to add a duplicate is silently ignored. Sets excel at tracking membership: unique visitors, active session IDs, feature flags enabled for an account, or any group where you need fast O(1) existence checks and don't care about order.

***

### SADD

Adds one or more members to the set stored at `key`. Members that already belong to the set are ignored. If `key` does not exist, a new set is created.

**Syntax:** `SADD key member [member ...]`

```redis theme={null}
SADD tags "redis" "cache" "database"
# (integer) 3

SADD tags "cache"
# (integer) 0  (already a member, nothing added)

SADD tags "search" "vector"
# (integer) 2
```

**Returns:** Integer — the number of members that were newly added (duplicates are not counted).

***

### SREM

Removes one or more members from the set stored at `key`. Members that are not in the set are silently ignored.

**Syntax:** `SREM key member [member ...]`

```redis theme={null}
SADD roles "admin" "editor" "viewer"

SREM roles "editor"
# (integer) 1

SREM roles "superuser"
# (integer) 0  (member did not exist)
```

**Returns:** Integer — the number of members that were actually removed.

***

### SMEMBERS

Returns all members of the set stored at `key`. Because sets are unordered, the order of members in the response is not guaranteed.

**Syntax:** `SMEMBERS key`

```redis theme={null}
SADD fruits "apple" "banana" "cherry"

SMEMBERS fruits
# 1) "banana"
# 2) "cherry"
# 3) "apple"
```

**Returns:** Array of bulk strings containing every member. Returns an empty array if the key does not exist.

<Note>
  The order of elements returned by `SMEMBERS` is not deterministic. If you need a stable order, sort the result in your application layer.
</Note>

***

### SISMEMBER

Tests whether `member` belongs to the set stored at `key`.

**Syntax:** `SISMEMBER key member`

```redis theme={null}
SADD permissions "read" "write"

SISMEMBER permissions "read"
# (integer) 1

SISMEMBER permissions "delete"
# (integer) 0
```

**Returns:** `1` if the member exists in the set, `0` if it does not (or if the key does not exist).

***

### SCARD

Returns the cardinality (number of members) of the set stored at `key`.

**Syntax:** `SCARD key`

```redis theme={null}
SADD online_users "u1" "u2" "u3"

SCARD online_users
# (integer) 3

SCARD nonexistent
# (integer) 0
```

**Returns:** Integer — the number of members, or `0` if the key does not exist.

***

## Practical example: tracking unique visitors

Sets are a natural choice for daily unique-visitor counting. Each user ID is recorded at most once per day, and you can query the exact count at any time:

```redis theme={null}
# Record visits for January 1st
SADD visitors:2024-01-01 user1 user2 user3
# (integer) 3

# user2 visits again — duplicate is ignored
SADD visitors:2024-01-01 user2
# (integer) 0

# Check if a specific user visited
SISMEMBER visitors:2024-01-01 user2
# (integer) 1

SISMEMBER visitors:2024-01-01 user99
# (integer) 0

# Exact unique count
SCARD visitors:2024-01-01
# (integer) 3

# See all unique visitors
SMEMBERS visitors:2024-01-01
# 1) "user1"
# 2) "user2"
# 3) "user3"
```

<Tip>
  Combine `EXPIRE` with your visitor sets to automatically clean up old day-buckets. For example: `EXPIRE visitors:2024-01-01 604800` will remove the key after seven days.
</Tip>