العلاقات

{ name: "براء", profile: { bio: "مطوّر", avatar: "..." } }

{ name: "براء", phones: ["050...", "055..."] }

// posts
{ _id: 1, title: "مقال", authorId: 10 }

// students
{ _id: 1, name: "براء", courses: [101, 102] }
// courses
{ _id: 101, name: "Mongo" }

db.posts.aggregate([
  { $lookup: {
      from: "users", localField: "authorId",
      foreignField: "_id", as: "author"
  } }
])