ZCARD for set size in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the Redis command ZCARD do?

The ZCARD command returns the number of elements in a sorted set stored at a given key.

beginner

How do you use ZCARD to find the size of a sorted set named myset?

You run the command: ZCARD myset. It returns the count of elements in myset.

beginner

What type of Redis data structure does ZCARD work with?

ZCARD works only with sorted sets, which are collections of unique elements ordered by score.

intermediate

What will ZCARD return if the key does not exist?

If the key does not exist, ZCARD returns 0, meaning the sorted set is empty or missing.

intermediate

Can ZCARD be used on Redis sets or lists?

No, ZCARD only works on sorted sets. For regular sets, use SCARD, and for lists, use LLEN.

What does the Redis command ZCARD myset return?

A The number of elements in the sorted set <code>myset</code>

B The sum of scores in <code>myset</code>

C The first element in <code>myset</code>

D The last element in <code>myset</code>

ZCARD returns the count of elements in the sorted set.

If the key myset does not exist, what does ZCARD myset return?

A null

B An error

C 0

D 1

ZCARD returns 0 when the key does not exist.

Which Redis data type is ZCARD designed for?

A Sorted Set

B Set

C List

D Hash

ZCARD works only with sorted sets.

Which command should you use to get the size of a regular Redis set?

A ZCARD

B SCARD

C LLEN

D HGETALL

SCARD returns the number of elements in a regular set.

What will ZCARD return if the sorted set has 5 elements?

A 0

B An error

C The highest score

D 5

ZCARD returns the count of elements, which is 5 in this case.

Explain what the Redis command ZCARD does and when you would use it.

Think about counting items in a special ordered collection.

Describe the difference between ZCARD and SCARD in Redis.

Focus on the data structure each command works with.