A trigger is a stored PL/SQL block that is executed automatically when a particular event occurs. Triggers are used to enforce business rules and to maintain data integrity.
For example, you can create a trigger that is fired when an INSERT statement is issued on a particular table. The trigger can check to make sure that the data being inserted meets certain criteria before it is accepted into the table.
A schema in Oracle Database is a collection of logical structures of data, or schema objects. A schema is owned by a database user and has the same name as that user. For example, a user named “John” would have a schema also named “John”. The schema would contain all of John’s tables, views, sequences, stored procedures, and other database objects.
To create a user in Oracle Database, you need to use the CREATE USER command.
For example:
CREATE USER new_user
IDENTIFIED BY new_password
DEFAULT TABLESPACE users
TEMPORARY TABLESPACE temp
QUOTA 10M ON users;
This command will create a new user called “new_user” with a password of “new_password”. It will also assign the user a default tablespace of “users” and a temporary tablespace of “temp”. It will also assign the user a quota of 10MB on the “users” tablespace.
Oracle Database is an enterprise-level relational database management system (RDBMS) developed by Oracle Corporation. It is used to store, manage, and retrieve data for applications. Oracle Database is a powerful and feature-rich database platform that enables organizations to deploy and manage data-driven applications, including online transaction processing (OLTP), data warehousing (DW), and analytics.
SQL (Structured Query Language) is a language used to interact with databases. It is used to create, modify, and query databases. It is used to retrieve, add, delete, and update data stored in the database. For example, an SQL statement can be used to create a table, insert data into the table, update data in the table, or delete data from the table.
1. Tables: A table is a collection of related data stored in rows and columns. For example, an Employee table may contain columns for employee ID, name, salary, and department.
2. Views: A view is a virtual table that contains data from one or more tables. For example, a view can be created to display only the employees in the Sales department.
3. Indexes: An index is an optional structure associated with a table to speed up the retrieval of data. For example, an index can be created on the Employee table to quickly look up an employee’s record based on their employee ID.
4. Sequences: A sequence is a database object used to generate unique numeric values. For example, a sequence can be used to generate the next employee ID for a new hire.
5. Synonyms: A synonym is an alias for a database object. For example, a synonym can be created for the Employee table so that it can be referenced using a different name.
6. Stored Procedures: A stored procedure is a set of SQL commands that are stored in the database and can be executed as a single unit. For example, a stored procedure can be used to calculate the total salary for all employees in a given department.
7. Triggers: A trigger is a stored procedure that is executed automatically when a data manipulation event occurs. For example, a trigger can be used to automatically update the salary of an employee when their job title is changed.
Oracle Database uses a number of features to ensure data integrity, including:
1. Primary Keys: A primary key is a unique identifier for a row in a table. It ensures that each row is uniquely identified and helps to prevent duplicate data.
2. Foreign Keys: A foreign key is a column or group of columns in a table that references a primary key in another table. This helps to ensure that related data is consistent across multiple tables.
3. Constraints: Constraints are used to enforce certain data integrity rules. For example, a NOT NULL constraint prevents null values from being inserted into a column.
4. Triggers: Triggers are code that is executed when certain database events occur. They can be used to check data integrity and enforce business rules.
5. Indexes: Indexes can be used to quickly search for data and ensure that data is stored in a consistent format.
6. Encryption: Data can be encrypted to ensure that it is secure and can only be accessed by authorized users.
1. Reliability: Oracle Database is designed to provide reliable and consistent data storage and retrieval. For example, Oracle Database provides features like ACID (Atomicity, Consistency, Isolation, and Durability) compliance, transaction control, and data integrity.
2. Scalability: Oracle Database can easily scale up and down depending on the demands of the applications. For example, Oracle Database provides features like Automatic Storage Management (ASM) and Real Application Clusters (RAC) to scale up the database.
3. High Performance: Oracle Database is designed to handle large volumes of data with high throughput. For example, Oracle Database provides features like In-Memory Column Store, Partitioning, and Parallel Execution to improve performance.
4. Security: Oracle Database provides robust security features to protect data from unauthorized access. For example, Oracle Database provides features like encryption, authentication, and auditing to protect data from malicious attacks.
5. Manageability: Oracle Database provides a comprehensive set of tools to simplify database administration tasks. For example, Oracle Database provides features like Oracle Enterprise Manager and Oracle Database Configuration Assistant to simplify database administration.
The Oracle Database is a relational database management system (RDBMS) designed to store, organize, and retrieve data. It is used to store and manage large amounts of data in a secure and reliable environment. Oracle Database is used in a wide variety of applications, ranging from small business applications to enterprise applications.
For example, Oracle Database is used for managing customer information, product inventory, financial records, employee information, and more. It can also be used to store and manage large amounts of data such as text, images, audio, and video. Additionally, Oracle Database can be used to create applications that can be used to access and analyze data stored in the database.
1. Unique Index: A unique index is a type of index that ensures that all values stored in the index key are unique. For example, if you have a table with a column that stores employee IDs, you can create a unique index on that column to ensure that no two employees have the same ID.
2. Bitmap Index: A bitmap index is a type of index that uses a bitmap to store the index keys. Each bit in the bitmap corresponds to a value in the index key. For example, if you have a table with a column that stores gender (male or female), you can create a bitmap index on that column to quickly find all the males or females in the table.
3. Composite Index: A composite index is a type of index that is made up of multiple columns. For example, if you have a table with columns for first name, last name, and age, you can create a composite index on those three columns to quickly find all the records with a particular combination of first name, last name, and age.
4. Function-Based Index: A function-based index is a type of index that is based on a function or expression. For example, if you have a table with a column that stores dates, you can create a function-based index on that column to quickly find all the records with a particular date range.
5. Spatial Index: A spatial index is a type of index that is used to quickly find records that are related to a particular location. For example, if you have a table with columns for latitude and longitude, you can create a spatial index on those columns to quickly find all the records that are within a certain distance of a particular location.
1. Heap-Organized Tables: These are the most common type of tables in Oracle. They are organized as a heap, which means that data rows are stored in an unordered fashion. For example, a table named “EMPLOYEES” can be created with the following command:
CREATE TABLE employees (
employee_id INTEGER,
first_name VARCHAR2(50),
last_name VARCHAR2(50),
email VARCHAR2(50),
salary NUMBER
);
2. Index-Organized Tables: These tables are organized based on an index. This means that the data is stored in an ordered fashion based on the index key. For example, a table named “ORDERS” can be created with the following command:
CREATE TABLE orders (
order_id INTEGER,
customer_id INTEGER,
order_date DATE,
order_total NUMBER,
CONSTRAINT orders_pk PRIMARY KEY(order_id)
) ORGANIZATION INDEX;
3. Clustered Tables: These tables are organized based on a cluster key. This means that the data is stored in an ordered fashion based on the cluster key. For example, a table named “PRODUCTS” can be created with the following command:
CREATE TABLE products (
product_id INTEGER,
product_name VARCHAR2(50),
product_price NUMBER,
CONSTRAINT products_pk PRIMARY KEY(product_id)
) CLUSTER product_cluster(product_name);
4. Temporary Tables: These tables are used to store temporary data. They are usually created and populated with data for a specific purpose and then dropped when no longer needed. For example, a table named “TEMP_DATA” can be created with the following command:
CREATE GLOBAL TEMPORARY TABLE temp_data (
data_id INTEGER,
data_value VARCHAR2(50)
);
Vaibhav Kothia