LEFT JOIN или...

select o.fid_d, o.numbox, o.numych, o.indexoper, o.obozdok, o.kodoper, o.nameoper, o.equipment1, o.id, o.kodobor, o.equipment2, o.yt, t.kod, t.classjob, t.vremy
    from 
    op_all o left join time_svr t on (o.fid_d = t.idfile) and (t.fidp=0) and (o.id = t.fidop)
    where o.fid_d = :file_id

for select numbox, numych, indexoper, obozdok, kodoper, nameoper, equipment1, id, kodobor, equipment2, yt 
     from op_all
     where (fid_d=:file_id)   
  into  :box, :ych,  :ind, :obozdok, :kodoper, :name, :equipment1, :fidop, :kodobor, :equipment2, :yt
    do begin
           KOD=null;
           CLASSJOB=null;
           VREMY=null;
           select kod, classjob, vremy from time_svr
           where (idfile=:file_id and fidop=:fidop and fidp=0)
           into :KOD, :CLASSJOB, :VREMY;
         suspend;
        end;

select ...
    from  op_all o left join time_svr t on (...)
    where o.fid_d = :file_id

for select ...    from op_all   where (fid_d=:file_id)    into  ...
   do begin
           ...
           select ...... from time_svr into ...
         suspend;
        end;