[Koha] Koha reports, include cataloguer

[Paul]

I am trying to "customize" some of our MySQL reports, to include the 
cataloguer who made the entry, with:

SELECT whatever.... FROM biblio
whatever FROM items
action_logs.user FROM action_logs
RIGHT JOIN biblioitems ON biblio.biblionumber = biblioitems.biblionumber
LEFT JOIN items ON biblio.biblionumber = items.biblionumber
WHERE whatever

but need a JOIN clause for action_logs  (could be RIGHT? timestamp? = 
?)  Without the third line the report is fully functional.

Could someone kindly assist?

Thanks and best regards,
Paul