How to select only the earliest date per group

Question

I am looking for a way to select only the lines with the earliest date per order-operation line. So in this case let's say that the database is called orderlines and it looks like :

I am looking for a way to select the earliest date per Orderopr line so per 123-10, 123-20, 124-10 etc. For some reaso I do not succeed in selecting only the earliest dates....

Answer 1

Check one on typical solutions:

select [order], operation, Orderopr, [date]
from 
(
   select *, row_number() over (partition by [order], operation order by [date]) n
   from orderlines
) o
where n = 1
order by [order], operation