ZADD for adding scored members in Redis

Introduction

ZADD lets you add items with scores to a sorted list in Redis. This helps keep things in order by score.

When you want to keep a leaderboard with player scores.

When you need to store tasks with priorities and get them sorted.

When you want to track items by time or rating and retrieve them in order.

When you want to add new members to a sorted set with their scores.

Syntax

Redis

ZADD key [NX|XX] [CH] [INCR] score member [score member ...]

key is the name of the sorted set.

You add one or more score member pairs to the set.

Examples

Adds 'player1' with score 100 to the 'leaderboard' sorted set.

Redis

ZADD leaderboard 100 player1

Adds two members 'taskA' with score 5 and 'taskB' with score 10 in one command.

Redis

ZADD tasks 5 taskA 10 taskB

Adds 'player2' with score 150 only if 'player2' does not already exist in 'leaderboard'.

Redis

ZADD leaderboard NX 150 player2

Sample Program

This adds three players with scores to the 'leaderboard' and then lists all players with their scores in order.

Redis

ZADD leaderboard 50 Alice
ZADD leaderboard 70 Bob
ZADD leaderboard 60 Charlie
ZRANGE leaderboard 0 -1 WITHSCORES

Important Notes

ZADD returns the number of new members added, not counting updated scores.

Scores are numbers and can be decimals.

Use ZRANGE with WITHSCORES to see members and their scores.

Summary

ZADD adds members with scores to a sorted set.

It keeps members sorted by score automatically.

You can add multiple members at once.