Gem tid mellem registreringer

Det ville være nyttigt, hvis du forberedte eksempeltabel og dataindsættelser.
Læs dette link for at lære, hvorfor det er så vigtigt, hvis du vil have hjælp :http://tkyte.blogspot.com/2005/06/how-to-ask-questions.html

Denne gang har jeg lavet det til dig, klik på dette link: http://sqlfiddle.com/#!2/9719a/2

Og prøv denne forespørgsel (du finder denne forespørgsel sammen med eksempeldata under ovenstående link) :

select alias1.*,
       timestampdiff( second, previous_viewed_at, viewed_at ) 
         as time_between_viewings
from (
select alias.*,
       (
         select viewed_at from (
             select
             ( select count(*) from asset_usages y
                where x.asset_id = y.asset_id 
                and y.viewed_at < x.viewed_at
              ) as rn,
              x.* 
              from asset_usages x
          ) xyz
          where xyz.asset_id = alias.asset_id 
               and xyz.rn = alias.rn - 1
       ) previous_viewed_at
from (
  select
    ( select count(*) from asset_usages y
      where x.asset_id = y.asset_id 
        and y.viewed_at < x.viewed_at
    ) as rn,
    x.* 
  from asset_usages x
) alias
) alias1;