MongoDB join
To‘plamlarga qo‘shiling
MongoDB relyatsion ma’lumotlar bazasi emas, lekin siz chap tashqi birlashmani amalga oshirishingiz mumkin
$lookup bosqichi yordamida.
$lookup bosqichi joriy to‘plamga qaysi to‘plamni qo‘shmoqchi ekaningizni va qaysi maydonlar mos kelishi kerakligini belgilash imkonini beradi.
Sizda "orders" to‘plami va "products" to‘plami bor deb hisoblang:
orders
[
{ _id: 1, product_id:
154, status: 1 }
]
mahsulotlar
[
{ _id: 154, name:
'Chocolate Heaven' },
{ _id: 155, name: 'Tasty Lemons' },
{
_id: 156, name: 'Vanilla Dreams' }
]
Misol
Mos “products” hujjat(lar)ini “orders” to‘plamiga qo‘shing:
let MongoClient = require('mongodb').MongoClient;
let url = "mongodb://127.0.0.1:27017/";
MongoClient.connect(url, function(err, db) {
if (err) throw err;
let dbo = db.db("mydb");
dbo.collection('orders').aggregate([
{ $lookup:
{
from: 'products',
localField: 'product_id',
foreignField: '_id',
as: 'orderdetails'
}
}
]).toArray(function(err,
res) {
if (err) throw err;
console.log(JSON.stringify(res));
db.close();
});
});
Misolni ishga tushirish »
Yuqoridagi kodni "demo_mongodb_join.js" nomli faylga saqlang va faylni ishga tushiring:
"demo_mongodb_join.js" ni ishga tushiring
C:\Users\Your Name>node demo_mongodb_join.js
Bu sizga bu natijani beradi:
[
{ "_id": 1, "product_id":
154, "status": 1, "orderdetails": [
{ "_id": 154, "name":
"Chocolate Heaven" } ]
}
]
Yuqoridagi natijadan ko‘rinib turibdiki, products to‘plamidagi mos hujjat orders to‘plamiga massiv sifatida kiritilgan.
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