Dubbele waarden elimineren op basis van slechts één kolom van de tabel

Dit is waar de vensterfunctie row_number() komt van pas:

SELECT s.siteName, s.siteIP, h.date
FROM sites s INNER JOIN
     (select h.*, row_number() over (partition by siteName order by date desc) as seqnum
      from history h
     ) h
    ON s.siteName = h.siteName and seqnum = 1
ORDER BY s.siteName, h.date