如何在mongodbmo中建立多对多关系

我刚刚开始学习MongoDB。 有人能介绍一下如何用mongodb实现这个例子吗

榜样

# Here are my categories
> hmset category:1 name cinema  ... more fields ...
> hmset category:2 name music   ... more fields ...
> hmset category:3 name sports  ... more fields ...
> hmset category:4 name nature  ... more fields ...

# Here are my users
> hmset user:1 name Jack   ... more fields ...
> hmset user:2 name John   ... more fields ...
> hmset 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

---

在MongoDB中，您可以选择预加入数据，因此可以将文档放在以下位置：

user : "John",
categories : ["music", "nature"]

还有一个放置引用的选项（更像RDBMS）：

这基本上取决于您的数据访问模式。因此，如果您基本上只检索与用户相关的类别，那么第一种情况应该是好的，否则，您可以考虑第二种情况，对用户和类别有不同的集合，然后引用它们，它们会出现如下情况，例如：

var category = { _id: "music"
            , name: "Musical Category"
            , users: ["jack", "julia", "john"] }
var user = { _id: "jack", name: "Jack", categories: ["music"]}
db.categories.save(category)
db.users.save(user)

db.categories.find({_id: {$in: user.categories}}) // categories for user
db.users.find({_id: {$in: category.users}}) // users for category

但我刚刚谈到了模式设计的主题。您必须分析基数和数据访问模式，以获得可靠的设计。 以下来自Mongo的帖子给出了很好的解释，并举例说明：

---

从手册中：

谢谢！那很有趣

var category = { _id: "music"
            , name: "Musical Category"
            , users: ["jack", "julia", "john"] }
var user = { _id: "jack", name: "Jack", categories: ["music"]}
db.categories.save(category)
db.users.save(user)

db.categories.find({_id: {$in: user.categories}}) // categories for user
db.users.find({_id: {$in: category.users}}) // users for category