Oracle® Database 2 Day DBA 11g Release 1 (11.1) Part Number B28301-03 |
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A schema is a collection of database objects. A schema is owned by a database user and shares the same name as the user. Schema objects are logical structures created by users. Some objects, such as tables or indexes, hold data. Other objects, such as views or synonyms, consist of a definition only.
Note:
There is no relationship between a tablespace and a schema. Objects in the same schema can use storage in different tablespaces, and a tablespace can contain data from different schemas.Naming Schema Objects
Every object in the database belongs to one schema and has a unique name within that schema. Multiple database objects can share the same name, if they are in different schemas. You can use the schema name to unambiguously refer to objects. For example, hr.employees
refers to the table named employees
in the hr
schema. (The employees
table is owned by hr
.) The terms database object and schema object are used interchangeably.
When you create a database object, you must ensure that you create it in the intended schema. One way to do this is to log in to the database as the user who owns the schema and then create the object. Generally, you place all the objects that belong to a single application in the same schema.
A schema object name must abide by certain rules. In addition to being unique within a schema, a schema object name cannot be longer than 30 bytes and must begin with a letter. If you attempt to create an object with a name that violates any of these rules, the database raises an error.
The Show SQL Button
You can create and manipulate schema objects with SQL or with Oracle Enterprise Manager Database Control (Database Control).
When creating schema objects using Database Control, you can click the Show SQL button to display the SQL statement that is the equivalent of the schema object properties that you specified with the graphical user interface. Database Control submits this SQL statement to create the schema object. This option shows the statement even if it is incomplete, so you must enter all specifications for the schema object to see the complete SQL statement that Database Control submits.
See Also:
Oracle Database SQL Language Reference for more detailed information about schema objects, object names, and data types