I'm not heavily involved with databases from a development point of view, is someone able to explain why Oracle is as successful as it is?
What sets them apart from what seems like a plethora of other DB systems?
The one I miss most is resource constraints on queries. It's nice to be able to guarantee that some queries will get more resources than others.
On the other hand, Oracle's SQL dialect is (or was, I stopped using it about 5 years ago) full of frustrating backwardness. No boolean type, so you get a mix of CHAR(1)s or INTs, depending on the prevailing DBA's opinion. And there's no serial or autoincrementing type, so for every table you wind up copying and pasting the same code over and over (create index, create sequence, insert trigger, update trigger).
The most head-scratching part is that you can find apologists for these flaws.
We have a lot of applications running on Oracle databases at my company, and therefore a lot of Oracle DBAs.
Now they prefer MariaDB or PostgreSQL for most new projects because Oracle has become too aggressive with their business practices, pricing and audits.
But now the DBAs must learn PostgreSQL and that requires some non trivial effort on their part to become as proficient as they were with Oracle.