ZADD for adding scored members in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the Redis command ZADD do?

The ZADD command adds one or more members with scores to a sorted set in Redis. It keeps the set ordered by score.

beginner

How do you add a member with score 10 to a sorted set named players using ZADD?

Use the command: ZADD players 10 member_name. This adds member_name with score 10 to the players sorted set.

intermediate

What happens if you add a member that already exists in the sorted set with a new score using ZADD?

The member's score is updated to the new score you provide. The sorted set reorders itself based on the updated score.

intermediate

Can ZADD add multiple members at once? How?

Yes. You can add multiple members by listing score-member pairs: ZADD key score1 member1 score2 member2 ....

intermediate

What does the return value of ZADD represent?

It returns the number of new members added to the sorted set, not counting members whose scores were updated.

What type of Redis data structure does ZADD work with?

A Hashes

B Lists

C Sorted sets

D Strings

ZADD adds members with scores to sorted sets only.

What happens if you use ZADD to add a member that already exists with a different score?

A The member is ignored

B The member's score is updated

C An error is returned

D The member is duplicated

The existing member's score is updated to the new score.

Which of these is the correct syntax to add two members with scores to a sorted set named game?

A ZADD game member1 10 member2 20

B ZADD game 10 20 member1 member2

C ZADD game member1 10, member2 20

D ZADD game 10 member1 20 member2

The correct syntax is ZADD key score1 member1 score2 member2.

What does ZADD return after adding members?

A Number of new members added

B The lowest score in the set

C The highest score in the set

D Total number of members in the set

ZADD returns how many new members were added, excluding updated ones.

If you want to add a member with score 5 to a sorted set called scores, which command is correct?

A ZADD scores 5 member

B ZADD scores member 5

C ZADD scores 5:member

D ZADD scores (5, member)

The score comes before the member name in the ZADD command.

Explain how the ZADD command works in Redis and what it is used for.

Think about adding and ordering members by numbers.

Describe the syntax of the ZADD command and how to add multiple members at once.

Remember the order: score then member, repeated for each.