Oracle Basic theory Note (i): Schema concepts

---oracle 10g

1. In an Oracle database, data objects are organized and managed in a pattern. A pattern is a collection of logical data structures or objects in a series.

2. The pattern corresponds to the user name, a pattern can only correspond to one user, and the schema name is the same as the name of the user, in general, the database objects created by the user are stored in the same name mode.

The name of the data object must be unique in the same mode. Data objects in different schemas can be the same.

For example: User UserA creates a test table object in the database, the test table is placed in UserA mode. The user UserB creates the test table object, which is placed in UserB mode.

3. By default, a user-referenced object is a reference to an object in a pattern of the same name, and if you want to refer to an object in another schema, you must precede the reference object with the object's owning pattern

For example:

User UserA under the test table, the user UserB under the test table, by default, the user UserA access the test table, direct SELECT * from Test, but to access the test under UserB, select * from Userb.test;

Note: Although the schemas and users in the database correspond to one by one, the user and schema are two completely different concepts.

Please refer to http://database.51cto.com/art/201010/231679.htm

Not all objects in the Oracle database are schema objects. tables, indexes, indexed tables, partitioned tables, materialized views, views, database connections, sequences, synonyms, packages, stored functions, procedures, Java classes, and so on, are specific patterns, called pattern objects.

Table spaces, users, roles, directories, profiles, contexts, and so on are not part of any schema, called non-object mode

Oracle Basic theory Note (i): Schema concepts