11-3

Database Objects

An Oracle database can contain multiple

data structures

. Each structure should be

outlined in the database design so that it can be created during the build stage of
database development.

•

Table

: Stores data

•

View:

Subset of data from one or more tables

•

Sequence:

Numeric value generator

•

Index:

Improves the performance of some queries

•

Synonym:

Gives alternative names to objects

Oracle9i Table Structures

•

Tables can be created at any time, even while users are using the database.

•

You do not need to specify the size of any table. The size is ultimately defined by
the amount of space allocated to the database as a whole. It is important, however,
to estimate how much space a table will use over time.

•

Table structure can be modified online.

Note: More database objects are available but are not covered in this course.

Instructor Note

Tables can have up to 1,000 columns and must conform to standard database object-
naming conventions.
Column definitions can be omitted when using the AS subquery clause. Tables are

created without data unless a query is specified. Rows are usually added by using
INSERT statements.

Introduction to Oracle9i: SQL 11-2