查询性能和调优

Question

要优化Oracle Query。 选择一个月的数据，大约需要24-26秒才能显示数据。 是否有可能对其进行优化和完善，并且花费的时间少于5到10秒。 非常感谢您的反馈。

select eutrancellfdd,
       startdate,
       max(connected_users)
from
(select eutrancellfdd,
        startdate,
        starthour,
        Round((case when pmrrcconnlevsamp_sum = 0 then 0
                 else (pmrrcconnlevsum/pmrrcconnlevsamp_sum) end),0) as connected_users
 from tblericsson)
group by eutrancellfdd, startdate
Having startdate between to_date('03/01/2015','MM/DD/YYYY') 
  AND to_date('04/01/2015','MM/DD/YYYY')
  and eutrancellfdd='L0253401'
order by startdate asc;      

Answer 1

尝试使用此查询。 另外，检查eutrancellfdd和startdate列上是否有索引。

select eutrancellfdd,
       startdate,
       max(Round((case when pmrrcconnlevsamp_sum = 0 then 0
                 else (pmrrcconnlevsum/pmrrcconnlevsamp_sum) end),0))
from
where startdate between to_date('03/01/2015','MM/DD/YYYY') 
      AND to_date('04/01/2015','MM/DD/YYYY')
      and eutrancellfdd='L0253401'
group by eutrancellfdd, startdate
order by startdate asc;