How to Use SINTER in Redis: Syntax and Examples

Use the SINTER command in Redis to find the common members between two or more sets. It returns the members that exist in all specified sets as a result.

Syntax

The SINTER command syntax is simple. You provide the names of two or more sets, and Redis returns the members common to all those sets.

• SINTER key1 key2 [key3 ...]: Returns the intersection of the sets stored at the given keys.

If any key does not exist, it is treated as an empty set, so the result will be empty.

redis

SINTER key1 key2 [key3 ...]

Example

This example shows how to use SINTER to find common elements between two sets named fruits and tropical.

redis

SADD fruits apple banana orange mango
SADD tropical mango pineapple banana
SINTER fruits tropical

Output

1) "banana"
2) "mango"

Common Pitfalls

Common mistakes when using SINTER include:

• Using keys that do not exist, which results in an empty intersection.
• Confusing SINTER with SUNION which returns all unique members from all sets.
• Expecting SINTER to modify the sets; it only returns the result without changing the original sets.

redis

SINTER fruits unknown_set

# Correct usage with existing sets
SINTER fruits tropical

Quick Reference

Command	Description
SINTER key1 key2 ...	Returns members common to all specified sets
SADD key member [member ...]	Adds members to a set
SMEMBERS key	Returns all members of a set
SUNION key1 key2 ...	Returns all unique members from all sets

Key Takeaways

SINTER returns members common to all given sets without modifying them.

If any set key does not exist, the result is an empty set.

Use SADD to add members before using SINTER to find intersections.

Do not confuse SINTER with SUNION; they serve different purposes.