set @namespace = 10;

set @slashnum = 2;

select * from page where page_namespace = @namespace and not exists (select 1 from page a where a.page_namespace = @namespace and a.page_title = SUBSTRING_INDEX(page.page_title,"/",@slashnum)) 

-- These should be cleaned up someday

and (@namespace != 10 or 

     (page_title not like "%/meta/%"

    and page_title not like "Alberta_provincial_election,%" 

    and page_title not like "British_Columbia_provincial_election,%"

    and page_title not like "Canadian_federal_election,%" ))

and (@namespace != 828 or 

    (page_title not like "Sandbox/%"

    and page_title not like "User:%"

     and (@slashnum != 2 or page_title not like "Location_map/data/%")))

limit 10000;