previousNext.scala

def prevNext = {        
        SQL(
            """
                (
                    select *, 'next' as pos from post 
                    where postedAt < {date} order by postedAt desc limit 1
                )
                    union
                (
                    select *, 'prev' as pos from post 
                    where postedAt > {date} order by postedAt asc limit 1
                )

                order by postedAt desc

            """
        ).on("date" -> postedAt).as( 
            opt('pos.is("prev")~>Post.on("")) ~ opt('pos.is("next")~>Post.on("")) 
        )
    }