我想知道高级mongodb聚合

Question

我想知道如何使此MySQL查询的MongoDB查询相同

"SELECT * FROM `folders` `F` JOIN `files` `I` ON I._id IN F.filesId;"

Answer 1

db.folders.aggregate([
{ 
    $lookup: { 
        from: "files",
        localField: "_id", 
        foreignField: "filesId", //_id is ObjectId() so  filesId fields on 
        as: "docs"               //  files table mustbe ObjectId Save
    } 
}
])

“ https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/”