SELECT page_namespace, page_title, SUBSTRING_INDEX(page_title,'/À_faire',1)

FROM page talkpage

WHERE talkpage.page_title LIKE '%/À_faire'

AND talkpage.page_namespace IN (1,5,11,15,101,119,711,829)

AND (NOT EXISTS (SELECT 1 FROM page mainpage

    WHERE mainpage.page_namespace = talkpage.page_namespace-1

    AND mainpage.page_title=SUBSTRING_INDEX(talkpage.page_title,'/À_faire',1))

 OR NOT EXISTS (SELECT 1 FROM page mainpage

    WHERE mainpage.page_namespace = talkpage.page_namespace

    AND mainpage.page_title=SUBSTRING_INDEX(talkpage.page_title,'/À_faire',1)))

ORDER BY page_namespace, page_title