How to find and delete duplicate records in Oracle Database

There are many ways you can do this - Below is one simple way to do it

select column_name, count(column_name)
from table
group by column_name
having count (column_name) > 1;

How to delete duplicate records in Oracle Database

delete from
   table_name a
where
   a.rowid >
   any (select b.rowid
   from
      table_name b
   where
      a.col1 = b.col1
   and
      a.col2 = b.col2
   );

Is Domain Driven Design (DDD) useful to your projects?

DDD is not for everyone and certainly not for all projects. To gain the most benefits when following DDD and deciding which projects will benefit from them, the following criteria can be used
1) You need a complex core domain that will be invested in over time
2) An iterative development process
3) Access to domain experts
4) Solid design principles required for refractoring
5) Sharp design sense
6) A focussed, motivated and experienced team

You need disciplined developers  who are willing to work with domain experts and understand the business rather than worry how they can wedge in the latest angular framework/tools into a project