MongoDB MongoDB Aggregation Left Outer Join with aggregation ( $Lookup)
Example
let col_1 = db.collection('col_1');
let col_2 = db.collection('col_2');
col_1 .aggregate([
{ $match: { "_id": 1 } },
{
$lookup: {
from: "col_2",
localField: "id",
foreignField: "id",
as: "new_document"
}
}
],function (err, result){
res.send(result);
});
This feature was newly released in the mongodb version 3.2 , which gives the user a stage to join one collection with the matching attributes from another collection
