●(1)以下SQL语句执行效率较低,大约在...... (1)以下SQL语句执行效率较低,大约在90分钟执行完毕 select distinct a.pulse_id,a.field_id, (select sum(kwh_val) from his_pbs_20041201 where pulse_id = a.pulse_id and to_number(to_char(unix_to_oracle(occur_time),'hh24'))=0 ) as v0, (select sum(raw_val) from his_pbs_20041201 where pulse_id = a.pulse_id and to_number(to_char(unix_to_oracle(occur_time),'hh24'))=0 ) as r0, (select sum(status) from his_pbs_20041201 where pulse_id = a.pulse_id and to_number(to_char(unix_to_oracle(occur_time),'hh24'))=0 ) as st0, from his_pbs_20041201 a where pulse_id = 164000029; (2)通过在SQL中加入Case语句,可以极大提高SQL的执行速度 select distinct a.pulse_id,a.field_id, sum(case to_number(to_char(unix_to_oracle(occur_time),'hh24')) when 0 then kwh_val else 0 end) as v0, sum(case to_number(to_char(unix_to_oracle(occur_time),'hh24')) when 0 then raw_val else 0 end) as r0, sum(case to_number(to_char(unix_to_oracle(occur_time),'hh24')) when 0 then status else 0 end) as st0, from his_pbs_20041201 a group by a.pulse_id,a.field_id; 以上两种取得数据透视表的方法在Oracle与Sql Server中均适用。第一种方法要耗时90分钟,第二种方法只需3分钟即可。 |
|小黑屋|最新主题|手机版|微赢网络技术论坛 ( 苏ICP备08020429号 )
GMT+8, 2024-9-30 09:21 , Processed in 0.085969 second(s), 12 queries , Gzip On, MemCache On.
Powered by Discuz! X3.5
© 2001-2023 Discuz! Team.