基于聚合的多集合

Question

我有 3 个表像

演员

actor_id: "1"
first_name: "Penelope"
last_name: "Guiness"

电影

film_id: "1"
title: "ABC"

Film_Actor

film_id: "1"
actor_id: "22"

我想要演员主演的电影（片名），喜欢

actor_id: "1"
title: {"ABC", "DEF", "GHI"}

在这种情况下我无法得到它，我刚刚实现的只是基于 2 个集合的聚合，如：

db.actor.aggregate ([
{
    $ lookup:
{
from: 'film_actor',
localField: 'actor_id',
foreignField: 'actor_id',
as: 'film_id'
}   }
])

Answer 1

首先，我认为您的数据模型存在问题。它看起来像一个 SQL 数据库，这不是使用 mongo.

的想法

但是如果你想这样做，你应该这样做：

db.actor.aggregate([
  {
    $lookup: {
      from: "film_actor", // the collection you are trying to match
      localField: "actor_id",
      foreignField: "actor_id",
      as: "film_actor"
    }
  },
  {
    $lookup: {
      from: "films", // the collection you are trying to match
      localField: "film_actor.film_id", // or '$film_actor.actor_id' if it does not work
      foreignField: "film_id",
      as: "film"
    }
  },
  {
    $group: {
      _id: "$actor_id",
      titles: {$push: "$film.title"}
    }
  }
]);

希望你觉得有用。

基于聚合的多集合

Aggregation based many collection

aggregation

mongodb

mongodb-query