Oracle Interview Question

First round was setup on April-16-2021. Had some basic questions on Java collections What and when do we use ArrayList and HashMap. How to insert data into and how to iterate on those two data structures. A couple of competitive coding questions, to come up with an optimal solution, pseudo code was sufficient A simple recursion based question Given a table, fetch the data by writing a SQL query. Question was in such a way that we utilise joins, aggregate functions Difference between POST and PATCH methods