如何在redis中建立多对多的关系 [英] how to have relations many to many in redis
问题描述
在关系型数据库中，我有一个用户表、一个类别表和一个用户类别表，它们可以建立多对多的关系.
In an relational database, i have an user table, an category table and an user-category table which do many to many relationship.
这个结构在Redis中的形式是什么?
What's the form of this structure in Redis?
推荐答案
对于 Redis，关系通常由集合表示.一套可以用表示一种单向关系，因此您需要为每个对象设置一组表示多对多关系.
With Redis, relationships are typically represented by sets. A set can be used to represent a one-way relationship, so you need one set per object to represent a many-to-many relationship.
尝试将关系数据库模型与 Redis 进行比较是非常无用的数据结构.使用 Redis，一切都以非规范化的方式存储.示例:
It is pretty useless to try to compare a relational database model to Redis data structures. With Redis, everything is stored in a denormalized way. Example:
# Here are my categories
> hset category:1 name cinema ... more fields ...
> hset category:2 name music ... more fields ...
> hset category:3 name sports ... more fields ...
> hset category:4 name nature ... more fields ...
# Here are my users
> hset user:1 name Jack ... more fields ...
> hset user:2 name John ... more fields ...
> hset user:3 name Julia ... more fields ...
# Let's establish the many-to-many relationship
# Jack likes cinema and sports
# John likes music and nature
# Julia likes cinema, music and nature
# For each category, we keep a set of reference on the users
> sadd category:1:users 1 3
> sadd category:2:users 2 3
> sadd category:3:users 1
> sadd category:4:users 2 3
# For each user, we keep a set of reference on the categories
> sadd user:1:categories 1 3
> sadd user:2:categories 2 4
> sadd user:3:categories 1 2 4
一旦我们有了这个数据结构，就可以很容易地使用集合代数来查询它:
Once we have this data structure, it is easy to query it using the set algebra:
# Categories of Julia
> smembers user:3:categories
1) "1"
2) "2"
3) "4"
# Users interested by music
> smembers category:2:users
1) "2"
2) "3"
# Users interested by both music and cinema
> sinter category:1:users category:2:users
1) "3"
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