SISMEMBER for membership check in Redis - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Check if a member exists in a Redis set

Given a Redis set named fruits containing apple, banana, and cherry, what is the output of SISMEMBER fruits banana?

Redis

SISMEMBER fruits banana

A 0

B 1

C nil

D error

💡 Hint

SISMEMBER returns 1 if the element is in the set, otherwise 0.

The command SISMEMBER fruits banana checks if banana is a member of the set fruits. Since banana is in the set, it returns 1.

❓ query_result

intermediate

Check membership of a non-existing element

What is the output of SISMEMBER fruits orange if the set fruits contains apple, banana, and cherry?

Redis

SISMEMBER fruits orange

A 1

B error

C nil

D 0

💡 Hint

SISMEMBER returns 0 if the element is not in the set.

The command SISMEMBER fruits orange checks if orange is in the set fruits. Since it is not, the command returns 0.

📝 Syntax

advanced

Identify the syntax error in SISMEMBER usage

Which option shows an incorrect syntax for the SISMEMBER command?

A SISMEMBER fruits

B SISMEMBER fruits cherry

C SISMEMBER fruits orange

D SISMEMBER fruits banana

💡 Hint

SISMEMBER requires exactly two arguments: the set key and the member to check.

Option A is missing the member argument. The correct syntax is SISMEMBER <key> <member>. Without the member, Redis returns a syntax error.

❓ query_result

advanced

Check membership on a non-existing set

What is the output of SISMEMBER colors red if the set colors does not exist in Redis?

Redis

SISMEMBER colors red

A 1

B nil

C 0

D error

💡 Hint

SISMEMBER returns 0 if the set does not exist.

If the set colors does not exist, Redis treats it as an empty set. Checking membership returns 0 because red is not a member.

🧠 Conceptual

expert

Understanding SISMEMBER return values

Which statement correctly describes the return values of the Redis SISMEMBER command?

A Returns 1 if the member exists, 0 if not, and 0 if the set does not exist

B Returns true if the member exists, false if not, and error if the set does not exist

C Returns 1 if the member exists in the set, 0 if not, and nil if the set does not exist

D Returns the member value if it exists, otherwise returns nil

💡 Hint

Think about how Redis treats non-existing sets for membership checks.

The SISMEMBER command returns 1 if the member is in the set, 0 if the member is not in the set, and also 0 if the set does not exist (treated as empty). It never returns nil or errors for non-existing sets.