Clubbing three queries that return mutually exclusive records
You can use aggregation like this:

select "Key", 
   MAX(CASE WHEN "Is_Orig" = 1 THEN "Value" END) "Orig Value",
   MAX(CASE WHEN "Is_Prev" = 1 THEN "Value" END) "Prev Value",
   MAX(CASE WHEN "Is_Curr" = 1 THEN "Value" END) "Curr Value"
from statistics
group by "Key"


The CASE statements select the value in each case and return NULL in the other cases. MAX is just to get that one value from the nulls.

Have a look at https://modern-sql.com/use-case/pivot for some background. It also refers to an Oracle specific feature called "modeling" that allows a similar thing.