SQL Server uses only PRIMARY partition by default My database has 2 partitions files: PRIMARY, DATABASE_ARCHIVED. A lot of tables have a column "archived". When archived is 1 row is in the DATABASE_ARCHIVED partition. When archived is 0 row is in the PRIMARY partition.

To improve performance I started to modify requests in the application by adding archive=0 in WHERE and JOIN.

select *
from myTable1 t1 
join myTable2 t2 
on t1.id = t2.t1id 
and t2.archive=0  
where t1.archive=0


But there are a lot of requests, and I might make mistake when typing and won't be able to test everything.

Is there a way to force all requests on the PRIMARY partition and use the ARCHIVED partition on demand? In the application there is a checkbox to see archived data or not.

Not checked : look for data in PRIMARY ONLY, checked : look in both partition.

Can I do this?
No, if you are talking about partitioned tables, sql uses the where clause to filter rows. if your query doesn't have the where clause it will return all rows.
if you can't test your changes you probably shouldn't be making them.