Class SQLFORM

       object --+            
                |            
html.XmlComponent --+        
                    |        
             html.DIV --+    
                        |    
                html.FORM --+
                            |
                           SQLFORM

SQLFORM is used to map a table (and a current record) into an HTML form

given a SQLTable stored in db.table

generates an insert form::

    SQLFORM(db.table)

generates an update form::

    record=db.table[some_id]
    SQLFORM(db.table, record)

generates an update with a delete button::

    SQLFORM(db.table, record, deletable=True)

if record is an int::

    record=db.table[record]

optional arguments:

:param fields: a list of fields that should be placed in the form,
    default is all.
:param labels: a dictionary with labels for each field, keys are the field
    names.
:param col3: a dictionary with content for an optional third column
        (right of each field). keys are field names.
:param linkto: the URL of a controller/function to access referencedby
    records
        see controller appadmin.py for examples
:param upload: the URL of a controller/function to download an uploaded file
        see controller appadmin.py for examples

any named optional attribute is passed to the <form> tag
        for example _class, _id, _style, _action, _method, etc.

SQLFORM(db.table,
       record=None,
       fields=['name'],
       labels={'name': 'Your name'},
       linkto=URL(r=request, f='table/db/')

similar FORM.accepts but also does insert, update or delete in DAL.
but if detect_record_change == True than:
  form.record_changed = False (record is properly validated/submitted)
  form.record_changed = True (record cannot be submitted because changed)
elseif detect_record_change == False than:
  form.record_changed = None