Overview of Datatypes

Each column value and constant in a SQL statement has a datatype, which is associated with a specific storage format, constraints, and a valid range of values. When you create a table, you must specify a datatype for each of its columns.
Oracle provides the following built-in datatypes:

• Character datatypes
• Numeric datatypes
• DATE datatype
• LOB datatypes
• RAW and LONG RAW datatypes
• ROWID and UROWID datatypes

New object types can be created from any built-in database types or any previously created object types, object references, and collection types. Metadata for user-defined types is stored in a schema available to SQL, PL/SQL, Java, and other published interfaces.
An object type differs from native SQL datatypes in that it is user-defined, and it specifies both the underlying persistent data (attributes) and the related behaviors (methods). Object types are abstractions of the real-world entities, for example, purchase orders.
Object types and related object-oriented features, such as variable-length arrays and nested tables, provide higher-level ways to organize and access data in the database. Underneath the object layer, data is still stored in columns and tables, but you can work with the data in terms of the real-world entities--customers and purchase orders, for example--that make the data meaningful. Instead of thinking in terms of columns and tables when you query the database, you can simply select a customer.

Overview of Globalization

Oracle databases can be deployed anywhere in the world, and a single instance of an Oracle database can be accessed by users across the globe. Information is presented to each user in the language and format specific to his or her location.
The Globalization Development Kit (GDK) simplifies the development process and reduces the cost of developing internet applications for a multilingual market. GDK lets a single program work with text in any language from anywhere in the world.