1. A view is a virtual table that is defined by a query on other tables. Views can restrict data access, simplify queries, provide data independence, and present different views of the same data. 2. Complex views can contain functions and join multiple tables, while simple views contain a query on one table. DML operations are not always allowed on complex views. 3. Top-N analysis uses a subquery to order results and an outer query to filter the top N rows using the ROWNUM pseudocolumn. This allows selecting the highest or lowest values from a column.