mongoDB 加入 MERN 堆栈项目

Question

我有两个 collection，我想加入他们。（请指导我使用 Mongo 3.6 语法）。产品：

 {
        "_id": "5b55c3b303d3a94e0c11e634",
        "createdAt": "2018-07-23T12:01:55.760Z",
        "updatedAt": "2018-07-23T12:01:55.760Z",
        "address": "1111 West Chicago Avenue, Chicago, IL 60642",
        "lang": "en",
        "poster": "/images/products/poster/pizzzzza.jpg",
        "new_price": 45,
        "off": 10,
        "old_price": 50,
        "summary": "10% Cash Back at Pie-Eyed Pizzeria",
        "title": "Pie-Eyed Pizzeria",
        "status": true,
        "category_id": "5b449e6b6f94bb4ab0b67b70"
    },
    {
        "_id": "5b55c34a03d3a94e0c11e631",
        "createdAt": "2018-07-23T12:00:10.409Z",
        "updatedAt": "2018-07-23T12:00:10.409Z",
        "address": "505 N. Lake Shore Dr. Suite #204, Chicago, IL 60611",
        "lang": "en",
        "poster": "/images/products/poster/asdasd.jpg",
        "new_price": 34,
        "off": 66,
        "old_price": 100,
        "summary": "No-Chip Mani-Pedi at MC Lash Studio (Up to 66% Off). Three Options Available.",
        "title": "MC Lash Studio",
        "status": true,
        "category_id": "5b449cf96f94bb4ab0b67b6b"
    }

我的第二个 collection 是 ProductDetails：

{
"_id" : ObjectId("5b55c3b703d3a94e0c11e635"),
"createdAt" : ISODate("2018-07-23T16:31:59.323+04:30"),
"updatedAt" : ISODate("2018-07-23T16:31:59.323+04:30"),
"location" : "",
"detail" : "Enter your Detail",
"terms_of_use" : "Enter terms of use",
"description" : "Enter your description",
"product_id" : "5b55c3b303d3a94e0c11e634"

},

{
"_id" : ObjectId("5b55c35003d3a94e0c11e632"),
"createdAt" : ISODate("2018-07-23T16:30:16.368+04:30"),
"updatedAt" : ISODate("2018-07-23T16:30:16.368+04:30"),
"location" : "",
"detail" : "Enter your Detail",
"terms_of_use" : "Enter terms of use",
"description" : "Enter your description",
"product_id" : "5b55c34a03d3a94e0c11e631"

}

我想要 mongodb

中的类似内容

select * from Products left join ProductDetails on Products._id = ProductDetails.product_id

我尝试了 $lookup 但我不知道如何将 "Products._id" 放入 $match.

import Products from '../models/ProductsModel.js';
export function getProductDetail(req, res, next){
  Products.aggregate(
    {
      $lookup:
      {
        from: "productsdetails",
          pipeline: [{$match:{product_id:Products._id}}],
            as: "product_detail"
      }
    })
}

Answer 1

您需要定义管道阶段，然后将它们传递给聚合函数，如下所示：

import Products from '../models/ProductsModel.js';
export function getProductDetail(req, res, next){
        // Pipeline stages definition 
        const pipeline = [
            { $match: {
                    "_id" : "5b55c3b303d3a94e0c11e634" // From you request params
                }
            },
            {$lookup: {
                    from: "ProductDetails",
                    localField: "_id",
                    foreignField: "product_id",
                    as: "details"
                }
            }
        ];
        Products.aggregate(pipeline).exec()
            .then((products) => {
                // Handle your response
            })
            .catch(err => {
                next(err);
            });
}

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