Purpose

Object types are defined using PL/SQL. Therefore, this section provides some general information but refers to Oracle Database PL/SQL Language Reference for details of syntax and semantics.

Use the CREATE TYPE statement to create the specification of an object type, a SQLJ object type, a named varying array (varray), a nested table type, or an incomplete object type. You create object types with the CREATE TYPE and the CREATE TYPE BODY statements. The CREATE TYPE statement specifies the name of the object type, its attributes, methods, and other properties. The CREATE TYPE BODY statement contains the code for the methods that implement the type.

An incomplete type is a type created by a forward type definition. It is called "incomplete" because it has a name but no attributes or methods. It can be referenced by other types, and so can be used to define types that refer to each other. However, you must fully specify the type before you can use it to create a table or an object column or a column of a nested table type.

Prerequisites

To create a type in your own schema, you must have the CREATE TYPE system privilege. To create a type in another user's schema, you must have the CREATE ANY TYPE system privilege. You can acquire these privileges explicitly or be granted them through a role.

To create a subtype, you must have the UNDER ANY TYPE system privilege or the UNDER object privilege on the supertype.

The owner of the type must be explicitly granted the EXECUTE object privilege in order to access all other types referenced within the definition of the type, or the type owner must be granted the EXECUTE ANY TYPE system privilege. The owner cannot obtain these privileges through roles.

If the type owner intends to grant other users access to the type, then the owner must be granted the EXECUTE object privilege on the referenced types with the GRANT OPTION or the EXECUTE ANY TYPE system privilege with the ADMIN OPTION. Otherwise, the type owner has insufficient privileges to grant access on the type to other users.

User-Defined Datatypes Declared as Non-Persistable Datatypes

You can specify a user-defined datatype as non-persistable when creating the datatype. Instances of non-persistable types cannot persist on disk. Perisistable data types include the following:

• ANSI-supported data types, for example NUMERIC, DECIMAL, REAL.

• Oracle built-in data types, for example NUMBER, VARCHAR2, TIMESTAMP.

• Oracle-supplied data types, for example ANYDATA, XML Type, ORDImage.

Rules For SQL User-Defined Data Types

• A persistable type cannot have attributes or elements of non-persistable types.

• A non-persistable type can have attributes or elements of both persistable and non-persistable types.

• A sub-type must inherit the persistence property from its super type.

• A REF type is persistable and can hold references only to objects of persistable types.

• You cannot persist instances of non-persistable types on disk. If you create a table with a type that has been declared as non-persistable, the CREATE TABLE statement will fail. The following operations will likewise fail:

  • Create or alter a relational table with columns of non-persistable types.

  • Create an object table with columns of non-persistable types.

  • Store instances of non-persistable types in an ANYDATA instance which is persisted on disk.

Syntax

Types are defined using PL/SQL. Therefore, the syntax diagram in this book shows only the SQL keywords. Refer to Oracle Database PL/SQL Language Reference for the PL/SQL syntax, semantics, and examples.

create_type::=

Description of the illustration create_type.eps

(plsql_type_source: See Oracle Database PL/SQL Language Reference.)

Semantics

OR REPLACE

Specify OR REPLACE to re-create the type if it already exists. Use this clause to change the definition of an existing type without first dropping it.

Users previously granted privileges on the re-created object type can use and reference the object type without being granted privileges again.

If any function-based indexes depend on the type, then Oracle Database marks the indexes DISABLED.

[ EDITIONABLE | NONEDITIONABLE ]

Use these clauses to specify whether the type is an editioned or noneditioned object if editioning is enabled for the schema object type TYPE in schema.The default is EDITIONABLE. For information about editioned and noneditioned objects, see Oracle Database Development Guide.

plsql_type_source

See Oracle Database PL/SQL Language Reference for the syntax and semantics of the plsql_type_source.