A sorted set associates a rank to each item in a set.

Sorted sets work in a similar way to sets, and they use similar commands, except S is now Z, for example:

• SADD -> ZADD
• SPOP -> ZPOP

But they are slightly different.

ZADD accepts a score:

ZADD names 1 "Flavio"
ZADD names 2 "Syd"
ZADD names 2 "Roger"

As you can see, values must still be unique, but now they are associated to a score.

The score does not have to be unique.

Items in a set are always sorted by the score.

This is very useful to implement some kind of data storage tool like (usual example) a leaderboard. Or to indicate the time some item was added, with a timestamp.

You can get the score of an item using ZRANK:

ZRANK names "Flavio"

List all items in a sorted set using ZRANGE, which works similarly to LRANGE in lists:

ZRANGE names 0 -1

Add WITHSCORES to also return the scores information:

You can increment the score of an item in the set using ZINCRBY.

See all the sorted sets commands here.

Lessons in this unit:

0:	Introduction
1:	Introduction to Redis
2:	How to install Redis
3:	First steps with Redis
4:	Redis Lists
5:	Using Redis Sets
6:	▶︎ How to use Redis Sorted Lists
7:	How to use Redis Hashes
8:	Redis Publish/subscribe
9:	How to use Redis from Node.js