Write query for selecting top 10 rows of an employee table?

Then he asked which topics I am comfortable with.I answered Dbms and Os.So he asked me few questions from Dbms 
1. What are different types of Dbms ?
2. What is the difference between Dbms and Rdbms
3. What is denormalization in dbms
4. What is stored procedure along with syntax?
Then he got into OOPS as the company is mainly focused on Java
1.explain concepts of OoPs with real life examples
2.what is abstract class , explain with a program?
3.What is constructor destructor?