One of the key characteristics of a set is that it does not allow duplicate values. When you add a new element to a set, if the element already exists, it won't be added again.

Sets are commonly used for storing unique values, such as user IDs, IP addresses, or any other data where duplicates must be avoided.

Practical Use of Sets in Redis

Basic Commands for Working with Sets

Redis sets come with several commands that make it easy to add, remove, and check elements

Adding and Removing Elements

The SADD command adds elements to a set, ignoring duplicates, and the SREM command removes elements from a set.

Code kopiëren
Collapse
9
1
2
SADD users "user1" "user2"  # adds "user1" and "user2" to the users set
SREM users "user1"  # removes "user1" from the users set

Checking for an Element and Retrieving All Elements

To check if a specific element is in a set, use the SISMEMBER command, which returns 1 if the element is present and 0 if it's not. To get all elements of the set, use the SMEMBERS command.

Code kopiëren
Collapse
9
1
2
SISMEMBER users "user2"  # checks if "user2" is in the users set (returns 1 or 0)
SMEMBERS users  # returns all elements of the users set

Getting Information About the Set

To get the number of elements in a set, use the SCARD command, which returns the number of elements in the set.

Code kopiëren
Collapse
SCARD users  # returns the number of elements in the users set

Operations with Multiple Sets

When working with multiple sets, you can use the commands SDIFF, SINTER, and SUNION — SDIFF returns elements that are in one set but not in the others, SINTER finds common elements across all specified sets, and SUNION returns the union of all elements from multiple sets.

Code kopiëren
Collapse
9
1
2
3
SDIFF set1 set2  # returns elements that are in `set1` but not in `set2`
SINTER set1 set2  # returns common elements between `set1` and `set2`
SUNION set1 set2  # returns the union of elements from `set1` and `set2`