Here is another 'source block' solution, this time in python. You could so
something  similar in elisp. Here I use the library of babel approach so
you can call it wherever you want.



#+name: csv
| ID | Name         | Titel / Title | Vorname / First Name | Nachname /
Surname | Institution           |
|  3 | Carol Carrot | Prof.         | Carol                | Carrot
    | University of Veg     |
|  1 | Alice Apple  | Fr./Ms.       | Alice                | Apple
     | Universität zum Apfel |
|  2 | Bob Birne    | Hr./Mr.       | Bob                  | Birne
     | Pear University       |


See https://orgmode.org/worg/org-contrib/babel/library-of-babel.html

#+name: signature-table
#+BEGIN_SRC python  :var data=csv :results value raw
results = [[surname, firstname, ""] for _, _, _, firstname, surname, _ in
data[1:]]

sorted_results = sorted(results,key=lambda row: row[1])

sorted_results = [[i + 1] + result for i, result in
enumerate(sorted_results)]

import tabulate
return tabulate.tabulate(sorted_results, ['#', 'Surname', 'First name',
'Signature'], tablefmt='orgtbl')
#+END_SRC



#+call: signature-table(data=csv)

#+RESULTS:
| # | Surname | First name | Signature |
|---+---------+------------+-----------|
| 1 | Apple   | Alice      |           |
| 2 | Birne   | Bob        |           |
| 3 | Carrot  | Carol      |           |


-----------------------------------
Professor John Kitchin
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
@johnkitchin
http://kitchingroup.cheme.cmu.edu



On Mon, Sep 16, 2019 at 8:48 AM Loris Bennett <loris.bennett@fu-berlin.de>
wrote:

> Hi John,
>
> Thanks - that's a nicely compact solution, albeit in the category
> 'source block' and in a language I'm not very skilled at :-)
>
> I realise that I have slightly misstated the problem.  The ID in the
> imported CSV is just a key from the database - I don't need it on the
> list of participants.  However, it would be nice to number the
> participants, who are sorted by surname.
>
> How would I insert a column which just numbers the row?
>
> Cheers,
>
> Loris
>
> John Kitchin <jkitchin@andrew.cmu.edu> writes:
>
> > You can do something like this:
> >
> > #+name: csv
> > | ID | Name         | Titel / Title | Vorname / First Name | Nachname /
> Surname | Institution           |
> > |  1 | Alice Apple  | Fr./Ms.       | Alice                | Apple
>         | Universität zum Apfel |
> > |  2 | Bob Birne    | Hr./Mr.       | Bob                  | Birne
>         | Pear University       |
> > |  3 | Carol Carrot | Prof.         | Carol                | Carrot
>        | University of Veg     |
> >
> > #+BEGIN_SRC emacs-lisp :var data=csv
> > (let ((table (mapcar (lambda (row) (list (nth 0 row) (nth 4 row) (nth 3
> row))) data)))
> >   (setf (car table) (append (car table) '("Signature")))
> >   table)
> > #+END_SRC
> >
> > #+RESULTS:
> > | ID | Nachname / Surname | Vorname / First Name | Signature |
> > |  1 | Apple              | Alice                |           |
> > |  2 | Birne              | Bob                  |           |
> > |  3 | Carrot             | Carol                |           |
> >
> > John
> >
> > -----------------------------------
> > Professor John Kitchin
> > Doherty Hall A207F
> > Department of Chemical Engineering
> > Carnegie Mellon University
> > Pittsburgh, PA 15213
> > 412-268-7803
> > @johnkitchin
> > http://kitchingroup.cheme.cmu.edu
> >
> > On Fri, Sep 13, 2019 at 9:36 AM Loris Bennett <
> loris.bennett@fu-berlin.de> wrote:
> >
> >  Hi,
> >
> >  I want to create a list of participants of an event which people can
> >  sign, so that I can record who actually turned up.
> >
> >  From the registration website I can download a CSV file and import it
> >  into and org file:
> >
> >  | ID | Name         | Titel / Title | Vorname / First Name | Nachname /
> Surname | Institution           |
> >  |  1 | Alice Apple  | Fr./Ms.       | Alice                | Apple
>         | Universität zum Apfel |
> >  |  2 | Bob Birne    | Hr./Mr.       | Bob                  | Birne
>         | Pear University       |
> >  |  3 | Carol Carrot | Prof.         | Carol                | Carrot
>          | University of Veg     |
> >
> >  I would like to reduce this to
> >
> >  | ID | Nachname / Surname | Vorname / First Name | Signature |
> >  |  1 | Apple              | Alice                |           |
> >  |  2 | Birne              | Bob                  |           |
> >  |  3 | Carrot             | Carol                |           |
> >
> >  and then print it out as a LaTeX table.
> >
> >  I can obviously write a source block of Python or R to do this, but can
> >  I manipulate the table more directly in Org?
> >
> >  Cheers,
> >
> >  Loris
> >
> >  --
> >  This signature is currently under construction.
> >
> --
> Dr. Loris Bennett (Mr.)
> ZEDAT, Freie Universität Berlin         Email loris.bennett@fu-berlin.de
>
>
>