How to create script to execute certain database function like updating a field one time?

I am coming from RDBMS(MS-SQL) world. I had SQL Server Managemnet Studio there to do my tasks. What I want to achieve is create a script which updates a field in document from collection. For example, Let say I have a collection “People” with documents having fields {id,firstName,lastName}. Now a new field added, called {ContactNo}, then I want to run one time script to update all previous documents with default value.
How do i achieve this?

@gschauhan Since you mentioned all documents, you can use the Documents() Index which Fauna provides. If you have more than 100000 documents, you should cursor to navigate through all pages.

  Paginate(Documents(Collection("People")), {
    size: 100000
  Lambda("x", Update(Select(['ref'], Get(Var("x"))), {
    data: {
      "newField": "Defaultvalue"

I have used bindings to filter null values