谁帮改改SQL语句，让更快执行
select   ENTERPRISE_NUM   ,
                SUM(CASE   WHEN   status   =   'A '     then   1   else   0   end)   ,  
                SUM(CASE   WHEN   status   =   'Z '     then   1   else   0   end)  
from     virtel_telrecord    
where   start_time> =   '2006-8-2     10:35:12 '
          and   sn   not   in
                          (select   b.sn   from   virtel_telrecord   b   ,virtel_telrecord   c
                            where   b.source   =   c.source   and   b.dest   =   c.dest    
                                      and   b.sn   !=c.sn   and   b.status   =   'Z '
                                      and     c.end_time   =   b.start_time)
group   by   ENTERPRISE_NUM  

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------解决方案--------------------
-- try

select a.ENTERPRISE_NUM ,
SUM(CASE WHEN a.status = 'A ' then 1 else 0 end) ,
SUM(CASE WHEN a.status = 'Z ' then 1 else 0 end)
from
virtel_telrecord a
left join
(select b.sn from virtel_telrecord b ,virtel_telrecord c
where b.source = c.source and b.dest = c.dest
and b.sn !=c.sn and b.status = 'Z '
and c.end_time = b.start_time) b
on a.sn = b.sn
where a.start_time > = '2006-8-2 10:35:12 ' and b.sn is null
group by a.ENTERPRISE_NUM