2 Tables and Table Clusters

This chapter provides an introduction to schema objects and discusses tables, which are the most common types of schema objects.

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This chapter contains the following sections:

• Introduction to Schema Objects
• Overview of Tables
• Overview of Table Clusters
• Overview of Attribute-Clustered Tables
• Overview of Temporary Tables
• Overview of External Tables
• Overview of Object Tables

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Introduction to Schema Objects

A database schema is a logical container for data structures, called schema objects. Examples of schema objects are tables and indexes. You create and manipulate schema objects with SQL.

A database user account has a password and specific database privileges. Each user account owns a single schema, which has the same name as the user. The schema contains the data for the user owning the schema. For example, the hr user account owns the hr schema, which contains schema objects such as the employees table. In a production database, the schema owner usually represents a database application rather than a person.

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Within a schema, each schema object of a particular type has a unique name. For example, hr.employees refers to the table employees in the hr schema. Figure 2-1 depicts a schema owner named hr and schema objects within the hr schema.

Figure 2-1 HR Schema
Description of “Figure 2-1 HR Schema”

This section contains the following topics:

• Schema Object Types
• Schema Object Storage
• Schema Object Dependencies
• SYS and SYSTEM Schemas
• Sample Schemas

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