This is why HN teems with NoSQL database nonsense and ideas like 100K rows is a scaling problem.
* https://en.wikipedia.org/wiki/Multics_Relational_Data_Store
Big companies build their software around the database, so once they have committed to a database vendor they are pretty well locked in. I don’t see any newer players directly competing with Oracle, but there are always competing products aimed at specific requirements.
Besides the database server Oracle also sells enterprise software applications. So do Microsoft, IBM, HPE, etc. Salesforce (founded by a former Oracle exec) is an example of a new-ish competitor. Salesforce of course uses Oracle.