Oracle Concepts and Architecture Database Structures 3

11. What is an Oracle view?
A view is a virtual table. Every view has a query attached to it. (The query is a SELECT statement that identifies the columns and rows of the table(s) the view uses.)

12. Do a view contain data?
Views do not contain or store data.

13. Can a view based on another view?
Yes.

14. What are the advantages of views?
- Provide an additional level of table security, by restricting access to a predetermined set of rows and columns of a table.
- Hide data complexity.
- Simplify commands for the user.
- Present the data in a different perspective from that of the base table.
- Store complex queries.

15. What is an Oracle sequence?
A sequence generates a serial list of unique numbers for numerical columns of a database's tables.