Do you still need this? There is no feedback from you.
Hi. In one table you have a value for every day of the month, and in the other you have value only on days when that value has changed, but it means that if on a given day there was no change, one should take last change so to say, to close the gaps with the most recent change.
I had some problems like that. I work as a DWH / BI / ETL Developer, working on Oracle Database. I have no clue about Apex, but i know Oracle, I know how to write this query on Oracle. I can write you this query, but you would have to see if that can be implemented in Apex. It can be written as a single query, with maybe few subqueries and using analytic functions, but without PL/SQL, procedures and cursors. There is also performance to think about, but it should not have significant negative impact.
If the query I write you can use in Apex (it will be a single query, no PL/SQL), then i can help you.