Difference b/w Primary key and unique key. Is unique key with not null constraint same as primary key? 2. Difference b/w Having and Where? 3. Can we decrement values in sequence? 4. What will you suggest if I want to delete a huge no. of records from an existing table. 5. Question about exceptions, how will you handle an exception about sequence if the maximum value of the sequence has been reached (if seq max value is 100000 and the next customer Id is 100001) 6. How do you check for Null values in a table? 7. How can you improve a query for faster retrieval of data? Some questions of sub nested queries. Asked 4-5 questions on Sequence. Asked few questions about functions and overloading. Some questions on Performance tuning and full table scan