How would you accomplish moving the value of one input rule to another?

Lets say you have a form with a textbox name.

The form populates from a DB tableA. What is the recommended way of saving it into DB tableB?

I experimented with the following:

1.

a!pickerFieldUsers(
  label: "Name",
  labelPosition: "ABOVE",
  value: if(isnull(ri!tableB.firstlastname), ri!tableA.requestaddedby, ri!tableB.firstlastname),
  saveInto: ri!tableB.firstlastname,
  readOnly: true,
  validations: {}
)

2. putting   a!save(ri!record.requestdateadded, now()), in the submit button etc.

Another idea was to keep the same rule input and handle it at "Write to DSE" in the process.