更新两个表的数据

Question

我试图通过将 t1 值乘以 t2 值来更新表中的某些值。这是我为更新数据而编写的查询。由于某些原因，更新值需要很长时间。我可以有一些简化的查询来更新相同的数据以提高查询的性能吗？

update dm_digital_media.dim_dummy sub
set sub.SUBS_ONE_TIME_TOTAL_USD = sub.SUBS_ONE_TIME_TOTAL_LOCAL_CURR * nvl(exch.exchange_rate,1) 
from dm_digital_media.dim_dummy sub1
inner join dm_digital_media.rate_dim exch on exch.exchange_source = sub1.currency
where sub.START_DATE < '2018-01-01'
  and exch.exchange_target = 'USD'
  and exch.begin_effect_date = '2018-01-01'
  and exch.exchange_period = 'Monthly';

Answer 1

你能试试下面的SQL吗？我用 CTE 稍微修改了一下。

with exch as (
select exchange_source,nvl(exch.exchange_rate,1) exchange_rate from dm_digital_media.rate_dim exch where  exch.exchange_target = 'USD' and exch.begin_effect_date = '2018-01-01' and exch.exchange_period = 'Monthly'
)
update dm_digital_media.dim_dummy sub set sub.SUBS_ONE_TIME_TOTAL_USD = sub.SUBS_ONE_TIME_TOTAL_LOCAL_CURR * exchange_rate
from dm_digital_media.dim_dummy sub1 
inner join exch on exch.exchange_source = sub1.currency 
where sub.START_DATE < '2018-01-01' ;