query - mongodb如何进行子查询

Question

用户collection，我是这么设计的：

User {
    uid: xx,
    name: xxx,
    description: xxxx,
    follow: ["uid1","uid2","uid3",...]
}

为了列出某个用户follow的所有人列表，我该如何写查询语句呢？

<uid1, name1, description1>
<uid2, name2, description2>
...

Answer 1

Don’t just think of mongodb as a schemeless SQL database. Mongodb does not have the concepts of subqueries and cross-table queries.

According to your description, if you want to get the detailed information list of everyone followed by a user, one way is to save all the information of these users in User:

User {
    uid: xx,
    name: xxx,
    description: xxxx,
    follow: ["uid1": {'name': 'xxx', 'description': 'desc1'},"uid2": {'name': 'zzz', 'description': 'desc2'},...]
}

Or you can use secondary query and check again in the code

db.User.find({'uid':{'$in': [uid1, uid2, uid3]}});