Datamart breaks when existing table is enhanced

Anonymous  I queried a table from sql server and set it up in the datamart.

Let's suppose that the following query was used when it was set up for the first time

select
      col1
      ,col2
      ,col3
from
    fact1 a 
outer apply (select * from dim1 b.....where)
where (predicate)
and exists (predicate) 
     

After a couple of days, I received an enhancement req from ops so that the query now becomes

select
      col1
      ,col2
      ,col3
from
    fact1 a 
outer apply (select * from dim1 b.....where)
where (predicate)
and exists (predicate) 
     
union all

select
      col1
      ,col2
      ,col3
from
    fact2 a 
outer apply (select * from dim2 b.....where)
where (predicate) and ..... and ...... and.....
and exists (predicate) 

Whenever I update/enhance/ my query I am facing challenges like this.