ZRANK and ZREVRANK for position in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the Redis command ZRANK do?

It returns the rank (position) of a member in a sorted set, ordered from the lowest to highest score, starting at 0.

beginner

How does ZREVRANK differ from ZRANK?

ZREVRANK returns the rank of a member in a sorted set ordered from highest to lowest score, starting at 0.

beginner

If a member is not found in the sorted set, what do ZRANK and ZREVRANK return?

Both commands return null (or nil) if the member does not exist in the sorted set.

intermediate

Example: Given a sorted set with members and scores: {"apple": 10, "banana": 20, "cherry": 15}, what is the result of ZRANK myset "cherry"?

The rank of "cherry" is 1 because the sorted order by score ascending is: apple(10), cherry(15), banana(20).

intermediate

Example: Using the same sorted set, what does ZREVRANK myset "cherry" return?

The rank of "cherry" is 1 because the descending order by score is: banana(20), cherry(15), apple(10).

What does ZRANK return if the member is the lowest scored in the sorted set?

A The highest rank number

B 1

C null

D 0

ZRANK ranks from lowest to highest score starting at 0, so the lowest scored member has rank 0.

Which command gives the rank starting from the highest score?

A ZRANGE

B ZRANK

C ZREVRANK

D ZADD

ZREVRANK ranks members from highest to lowest score.

If a member is not in the sorted set, what will ZREVRANK return?

A null

B 0

C The last rank

D An error

Both ZRANK and ZREVRANK return null if the member is missing.

Given sorted set scores: {a:5, b:10, c:15}, what is ZRANK myset "b"?

A 1

B null

C 2

D 0

Sorted ascending: a(5), b(10), c(15). "b" is at position 1.

What is the rank of the highest scored member using ZREVRANK?

A 1

B 0

C The last rank

D null

ZREVRANK starts ranking from highest score at 0.

Explain how ZRANK and ZREVRANK determine the position of a member in a Redis sorted set.

Think about the order of scores and what 0 means.

Describe a real-life example where you might use ZRANK and ZREVRANK in an application.

Consider games or scoring systems.