[Koha] Koha reports, include cataloguer

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