Data Definition Language (DDL)
The DDL commands let you create, replace, alter, drop, rename, and truncate database objects, permissions, and settings. A database instance is required before you can manipulate database objects. When you installed Oracle Database, the installation script created a clone of a sample database. Alternatively, the installation program could have used the CREATE command to build a database instance. After creating the database instance, you can then use the ALTER command to change settings for the instance or for given sessions. Sessions last the duration of a connection to the database instance.
The DDL section is organized into subsections and covers the following topics:
Managing tables and constraints