How to do inner joining in MongoDB?

Question

Is it possible to do SQL inner joins kind of stuff in MongoDB , well i know there is

$lookup

attribute in aggregation pipeline and

Answer 1

> show dbs
admin   0.000GB
config  0.000GB
local   0.002GB
> use local
switched to db local
> show collections
startup_log
test1
test2
> db.test2.aggregate([{
...    $lookup: {
...       from: "test1",
...       localField: "id",
...       foreignField: "id",
...       as: "aggTest"
...    }
... }])