title: mysql error code 1248
body: <p>I am getting an error code 1248 and have no idea why. Thanks in advance. </p>
  
  <pre><code>select substr(cbt,1,8) day, 
      max((delta_GTP_InDataPktGn+delta_GTP_OutDataPktGn))/900
  from 
  (
      select a.cbt, a.datetime, 
      a.GTP_InDataPktGn - b.GTP_InDataPktGn as delta_GTP_InDataPktGn,
      a.GTP_OutDataPktGn - b.GTP_OutDataPktGn as delta_GTP_OutDataPktGn
  
      from
          (   select cbt, STR_TO_DATE(substr(cbt,1,12),'%Y%m%d%H%i') as datetime, 
              GTP_InDataPktGn, 
              GTP_OutDataPktGn
              from sgsn_GTP 
          ) a
  
          right join 
          (
              select cbt, STR_TO_DATE(substr(cbt,1,12),'%Y%m%d%H%i') as datetime, 
              GTP_InDataPktGn, 
              GTP_OutDataPktGn
              from sgsn_GTP 
          ) 
       on a.datetime = addtime(b.datetime,"00:15:00")
  ) z
  
  where z.cbt between 20130429000000 and 20130430980000
  group by day
  </code></pre>