Can be the following query further optimized?

Question

I have the following SQL query and personally i can't find a way to optimize this further.
Do you agree with me?

This is the query:

select
   t1.queue,
   t.accountcode as agent,
   TIMESTAMPDIFF(SECOND, time1, t.calldate) as recall_time 
from
   daily_cdr t 
   inner join
      (
         select
            a.callid,
            a.data2 as caller,
            Cast(a.time as datetime) as time1,
            a.queuename as queue 
         from
            queue_log a 
            inner join
               queue_log b 
               on a.callid = b.callid 
         where
            a.event = "ENTERQUEUE" 
      )
      t1 
      on t.dst = t1.caller 
where
   disposition = "ANSWERED" 
   and billsec > 0 
   and t.calldate > t1.time1 
   and t.accountcode is not null 
group by
   uniqueid;

It will be executed on a 5.5.68-MariaDB instance.

I started from a query made by several subqueries.

The next is only a part of the initial query to give you an idea of how it was:

    select
    (
       select
          data2 
       from
          queue_log 
       where
          callid = t.callid 
          and event = "ENTERQUEUE") as caller,
          (
             select
                Cast(time as datetime) 
             from
                queue_log 
             where
                callid = t.callid 
                and event = "ENTERQUEUE"
          )
          as time1,
          (
             select
                queuename 
             from
                queue_log 
             where
                callid = t.callid 
                and event = "ENTERQUEUE"
          )
          as queue 
       from
          (
             select
                callid 
             from
                queue_log 
             where
                event in 
                (
                   "XITEMPTY",
                   "EXITWITHKEY",
                   "EXITWITHTIMEOUT",
                   "FULL",
                   "JOINEMPTY",
                   "JOINUNAVAIL",
                   "ABANDON"
                )
          )
          t

I think I've done a good enough job, but surely someone else could do better or has some important advice to share.

Answer 1

As suggested by @FanoFN and @danblack, the subquery isn't necessary so the query can be done in this way:

select
   t1.queuename,
   t.accountcode as agent,
   TIMESTAMPDIFF(SECOND, Cast(t1.time as datetime), t.calldate) as recall_time 
from
   daily_cdr t
inner join 
   queue_log t1
   on t.dst = t1.data2
where
   t1.event = "ENTERQUEUE"
   and t.disposition = "ANSWERED" 
   and t.billsec > 0 
   and t.calldate > Cast(t1.time as datetime) 
   and t.accountcode is not null 
group by
   t.uniqueid;