sql语句如下:
select registration,companynew,branchnew,roadlinenew,usedate from (select registration,companynew,branchnew,roadlinenew,usedate,row_number() over(partition by registration ORDER BY savetime desc) as xuhao from vehrecord) where xuhao =1 and usedate <= sysdate;
如下图所示,执行后cost数据较大,导致I/O也比较大,请教如何优化!
select registration,companynew,branchnew,roadlinenew,usedate from (select registration,companynew,branchnew,roadlinenew,usedate,row_number() over(partition by registration ORDER BY savetime desc) as xuhao from vehrecord) where xuhao =1 and usedate <= sysdate;
如下图所示,执行后cost数据较大,导致I/O也比较大,请教如何优化!
http://bbs.csdn.net/topics/391953247
我的回帖。
去掉子查询
over(partition by registration ORDER BY savetime desc)提到外查询
检查savetime, usedate索引