> * Set :hlines to "yes"
>
> `:hlines yes' should leave the horizontal line, but generates an error.
>
>   #+begin_src emacs-lisp :var data=table :results output :hlines yes
>   (mapc (lambda (item) (princ (format "UPDATE dim SET val=%s WHERE code='%s'\n"
>                                       (nth 1 item) (nth 0 item))))
>    data)
>   #+end_src

This is not a babel error, this is an error in your code block body,
which assumes that every element of `data' will be a list.  The symbol
`hline' is not a list.

>
> Finally, how am I then supposed to *ignore the header line*?  By adding
>
>   #+begin_src emacs-lisp
>   (setq table (cdr table))
>   #+end_src
>
> ?
>
> Do I have to do that explicitly in my code block, or is there an option for
> telling that to Babel?
>

Use the :colnames processing to strip the headings.

    #+begin_src emacs-lisp :var data=table :colnames yes
      data
    #+end_src

    #+RESULTS:
    : (("ABJ" 1) ("DEK" 2))

Best,

>
> Best regards,
>   Seb

-- 
Eric Schulte
https://cs.unm.edu/~eschulte
PGP: 0x614CA05D