Now I get two collections: coll01 and coll02.

And the structure of coll01 is like this:

{
  id: 01,
  name: "xxx",
  age: 30
}

and the structure of coll02 is like:

{
  id: 01,
  name: "XYZ"
  gender: "male"
}

The two id fields in the both collection are indices. And the numbers of documents in these two collections are same.

And what I want to do in traditional SQL is :

update coll01, coll02
set coll01.name = coll02.name
where coll01.id = coll02.id