It's currently not possible to cover that topic in one reply except to say that you would be taking a journey of a few years to cover all that would be involved.
Only your newest of the new would say this can be covered in a few paragraphs. For example I continue to encounter passwords stored in databases. This is in 99% of systems a very bad idea. How to handle that takes at least a few sessions in class.
As to database admin, that can be easy to complex. There is so much on the web about say, MySQL that only those that think one paragraph can explain it are missing out.
The information is out there now. Go get it.
to learn about security in terms of coding and also administrating in database