Differences between Oracle users and Models

Oracle users are an important concept in Oracle databases. The following describes the differences between Oracle users and models, and hopes to help you learn about Oracle users.

1) What is Oracle user ):
A user is a name defined in the database that can connect to and access objects.
Oracle users connect to databases and Access database objects. The user is used to connect to the database to access the database ).

2) What is schema ):
A schema is a collection of database objects (used by a user .).
Schema objects are the logical structures that directly refer to the database's data.
Mode is a collection of database objects. The schema object is the logical structure of the database data.
Divides database objects into different logical structures in different modes ).

3) differences between user and schema:
Schemas and users help database administrators manage database security.
A user is used to connect to a database object. The mode is used to create management objects. The mode is one-to-one with the user in oracle.
However, db2 is different. A db2 user can correspond to multiple modes. A db2 user is a system and must first obtain a system user to become a database user, that is, a database user is a system user, only the mode is similar to the database user. If you are interested, you can study it. This is unique to db2 ).

From the definition, we can see that schema is a set of database objects. To distinguish each set, we need to name this set, these names are the nodes similar to user names that we see in the Enterprise Manager Solution. These nodes similar to user names are actually a schema, which contains various objects such as tables, views, sequences, stored procedures, synonyms, indexes, clusters, and database links. A user generally corresponds to a schema. The schema name of the user is the same as the user name and serves as the user's default schema. This is why the schema names are database usernames in the Enterprise Manager Solution. You cannot create a new schema in an Oracle database. To create a schema, you can only create one user, but it is not used to create a schema). When creating a user, create a schem with the same name as the user name and use it as the default shcema for the user. That is to say, the number of schemas is the same as the number of users, and the schema names are one-to-one and the same as the names of users. All aliases that can be called schema as users are inaccurate, but it is easier to understand.

A user has a default schema, and Its schema name is the same as the user name. Of course, a user can also use other schemas. If we access a table without specifying which schema the table belongs to, the system will automatically add the default sheman name to the table. For example, when we access the database, we can access the emp table under the scott user through select * from emp; in fact, the complete Syntax of this SQL statement is select * from scott. emp. The full name of an object in the database is schema. object, not user. object. Similarly, if we do not specify the schema of the object when creating the object, the schema of the object is the default schema of the user. This is like a user has a default tablespace, but this user can also use other tablespaces. If we do not specify a tablespace when creating an object, the object is stored in the default tablespace, to store objects in other tablespaces, We need to specify the tablespace of the object when creating the object.
 

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