Database Concepts › Logical Database Description › Schemas

Schemas

A schema provides the description of the logical contents if a database. Schemas can describe a database in terms of:

• Tables- a relational database whose schema is defined using SQL Data Definition Language (DDL)
• Record Types- a network database whose schema is defined using a (non-SQL) Codasyl-based DDL

Only a database described by a non-SQL schema can be accessed using navigational DML.

A non-SQL schema defines the record types and sets that implement the entities and relationships within the database. The schema also identifies the logical areas into which the database is divided and assigns record types and system-owned indexes to areas.

The following diagram illustrates the contents of the schema for Commonweather Corporation's database.