How to Use SADD Command in Redis: Add Members to a Set

Use the SADD command in Redis to add one or more members to a set stored at a key. It creates the set if it does not exist and returns the number of new members added.

Syntax

The SADD command adds one or more members to a set stored at a given key. If the key does not exist, Redis creates a new set. The command returns the number of elements that were added to the set, excluding members that were already present.

• key: The name of the set.
• member [member ...]: One or more values to add to the set.

redis

SADD key member [member ...]

Example

This example shows how to add members to a set named fruits. It adds three fruits and then tries to add one that already exists.

redis

127.0.0.1:6379> SADD fruits apple banana cherry
(integer) 3
127.0.0.1:6379> SADD fruits banana orange
(integer) 1
127.0.0.1:6379> SMEMBERS fruits
1) "apple"
2) "banana"
3) "cherry"
4) "orange"

Output

(integer) 3
(integer) 1
1) "apple"
2) "banana"
3) "cherry"
4) "orange"

Common Pitfalls

Common mistakes when using SADD include:

• Trying to add duplicate members expecting the count to increase. Redis only counts new unique members.
• Using SADD on keys holding other data types causes errors.
• Not checking the return value to confirm how many members were actually added.

redis

127.0.0.1:6379> SET fruits "not a set"
OK
127.0.0.1:6379> SADD fruits apple
(error) WRONGTYPE Operation against a key holding the wrong kind of value

-- Correct usage:
127.0.0.1:6379> DEL fruits
(integer) 1
127.0.0.1:6379> SADD fruits apple
(integer) 1

Output

(error) WRONGTYPE Operation against a key holding the wrong kind of value
(integer) 1

Quick Reference

Command	Description
SADD key member [member ...]	Add one or more members to a set
SMEMBERS key	Get all members of the set
SREM key member	Remove a member from the set
SCARD key	Get the number of members in the set

Key Takeaways

Use SADD to add unique members to a Redis set; it creates the set if missing.

SADD returns the count of new members added, ignoring duplicates.

Avoid using SADD on keys holding non-set data types to prevent errors.

Check the return value to confirm how many members were actually added.

Use SMEMBERS to view all members of a set after adding.