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About Tables

The table is the basie unit of data storage in an Oracle database. It holds all user-accessible data. Each table is madę up of columns and rows. In the employees table, for example, there are columns called last_name and employee_id. Each row in

the table represents a different employee, and contains a value for last_name and employee_id.

When you create a table, you specify the table type, and define its columns and constraints. Constraints are rules that help preserve data integrity.

This section contains the following topics:

■About Table Types

■About Table Column Attributes

■About Table-Level Constraints