How can we use the schema in Oracle?

In Oracle, a Schema is a logical container used for organizing and managing database objects such as tables, views, indexes, etc. Each Schema has a unique name and multiple Schemas can be created in one database.

To utilize Oracle’s Schema, you first need to create one. You can create a Schema in Oracle using the following syntax:

CREATE USER schema_name IDENTIFIED BY password;

In which, schema_name is the name of the created Schema, and password is the password used to access the Schema.

After creating the Schema, you can use the following syntax to add database objects to the Schema.

CREATE TABLE schema_name.table_name (column1 datatype, column2 datatype, ...);

“Here, schema_name refers to the name of the schema where the table will be added, and table_name is the name of the table to be created.”

You can then use the following syntax to query, modify, or delete objects in the Schema.

SELECT * FROM schema_name.table_name;
UPDATE schema_name.table_name SET column1 = value WHERE condition;
DELETE FROM schema_name.table_name WHERE condition;

The schema_name is the name of the schema to be operated on, and the table_name is the name of the table to be operated on.

Furthermore, you can use the following syntax to create views, indexes, constraints, and other database objects in the Schema.

CREATE VIEW schema_name.view_name AS SELECT column1, column2, ... FROM schema_name.table_name;
CREATE INDEX index_name ON schema_name.table_name (column1, column2, ...);
ALTER TABLE schema_name.table_name ADD CONSTRAINT constraint_name PRIMARY KEY (column1, column2, ...);

其中，schema_name is the name of the Schema for the object to be created, view_name is the name of the view to be created, index_name is the name of the index to be created, and constraint_name is the name of the constraint to be created.

It is important to note that when using Schema, you should explicitly specify the Schema name in the SQL statement to clearly define the ownership relationship of the objects. For example, “SELECT * FROM schema_name.table_name”, where schema_name is the name of the Schema and table_name is the name of the table.