Edit records using Stateless Forms

Edit records using Stateless Forms

Could someone point me to where I can find out how I can use a stateless form to edit a record?
 
I feel that this must be such common requirement in most applications that there will already be some documentation on line, but I haven't spotted it yet.
 
What I envisage is that once the form is open there would be a way to launch a script (a button On Click?) that will fetch data from a record and populate the stateless form.  And then, of course, when you 'Submit' it needs to update the existng record ... not create a new one!
 
Alternatively, I could see that a special stateless form could be used to find the record and then launch a separate data input form.
 
I can see some challenges in how you find the record you want if there are duplicates in the fields, but I am sure this has been figured out!