两个数据库/表之间的持续时间更快

Question

The duration to the following query is around 8 mins. I am looking for the average business days between two dates and am using two db's and tables with one being a calendar table. Is there a more efficient way of making the duration for the following query faster?

select avg(datediff(e.column1, e.column2)) as 'diff' 
from DB1 e
inner join db2.table1 pd on e.column3 = pd.column1
where pd.calendar_day_in_week not in (1,7) 

Answer 1

Is e.column3 and pd.column1 indexed? I think is the join that makes query go slow. Try this

select avg(datediff(e.column1, e.column2)) as 'diff' 
from DB1 e
inner join (SELECT column1 FROM db2.table1 WHERE calendar_day_in_week not in (1,7)) AS pd on e.column3 = pd.column1

Do the where on the table1 first, so you get smaller chunk table for the join.