Introduction to Databases

Databases are essential for storing, managing, and retrieving data in applications. Below are three popular database management systems (DBMS) that are commonly used in software development: MySQL, PostgreSQL, and MongoDB. Each database has its strengths and is used based on the requirements of the project.

1. Introduction to MySQL

MySQL is one of the most popular open-source relational database management systems (RDBMS). It uses SQL (Structured Query Language) for querying and managing data. MySQL is well-suited for applications that need fast, reliable, and scalable databases.

Key Features of MySQL:

• ACID compliance: Ensures data integrity and reliability.
• Ease of Use: Simple to set up and use.
• High Performance: Handles high-speed transactions well.
• Replication: Supports master-slave replication for data redundancy.

Installation of MySQL on Ubuntu

1. Update package index:

   sudo apt update

2. Install MySQL Server:

   sudo apt install mysql-server

   you can login to mysql server by the command sudo mysql  , now change the default authentication  for root with the password of own .

   alter user 'root'@'localhost' identified with mysql_native_password by 'your_password';

   now password was change  and authentication method was replaced.

   exit from the mysql server by the command

   exit 

3. Secure MySQL Installation: After installation, it’s a good idea to secure the MySQL installation:

   sudo mysql_secure_installation

   This will prompt you to configure a root password and remove insecure default settings.

   enter the root password and press y for validation password.

   enter 0,1 or 2 according to you requirements for the password validation, Press y for the others default settings.

    

   now if you try to login with sudo mysql it will throw access denied now need to login with the user and password
    

   mysql -u root -p
   create database example_DB;
   show schemas;

   now create a new user and grant privileges to the particular database as

   create user 'user_name'@'localhost' identified with mysql_native_password by 'new_password';

   you can see the created user in mysql database's user table as

   use mysql;
   select user from user;

   now grant all privileges to database for the newly created user as 

   grant all on database_name.* to 'user_name'@'localhost';
   exit;

    

4. Check MySQL Status: To ensure MySQL is running properly, you can check the status:

   sudo systemctl status mysql

Install phpmyadmin 

phpmyadmin used php  so we have to have php in our server. install php through the command

sudo apt insall php

now, install phpmyadmin by running command 

sudo apt install phpmyadmin

 choose webserver for phpmyadmin better to go with apache2 . 

read doc and press Yes or No ( better to choose No

after successfully install you can open phpmyadmin in webbrower by running 

if you faced issue like while running phpmyadmin as in below

follow below setps

nano /etc/apache2/apache2.conf
# Then add the following line to the end of the file:
Include /etc/phpmyadmin/apache.conf
# Then paste in terminal: restart apache:
/etc/init.d/apache2 restart

2. Introduction to PostgreSQL

PostgreSQL is a powerful, open-source object-relational database system. Unlike MySQL, PostgreSQL is known for its focus on extensibility and standards compliance, as well as its support for advanced data types.

Key Features of PostgreSQL:

• ACID Compliance: Supports transactions and data integrity.
• Extensibility: Can handle custom data types, custom functions, and even advanced indexing methods.
• Concurrency: Uses Multi-Version Concurrency Control (MVCC) for handling multiple transactions efficiently.
• SQL and NoSQL: Supports both relational and NoSQL features like JSONB.

Installation of PostgreSQL on Ubuntu

1. Update package index:

   sudo apt update

2. Install PostgreSQL and client:

   sudo apt install postgresql postgresql-contrib

3. Check PostgreSQL Status: Verify that PostgreSQL is running:

   sudo systemctl status postgresql

4. Switch to the PostgreSQL User: PostgreSQL creates a default user postgres during installation. Switch to this user:

   sudo -i -u postgres

5. Access PostgreSQL Shell: You can enter the PostgreSQL shell by typing:

   psql

3. Introduction to MongoDB

MongoDB is a NoSQL database that stores data in a flexible, JSON-like format called BSON (Binary JSON). Unlike MySQL and PostgreSQL, MongoDB is designed for applications that need to handle large amounts of unstructured or semi-structured data.

Key Features of MongoDB:

• Schema-less: Allows for flexibility in data storage.
• High Availability: Built-in replication for fault tolerance.
• Scalability: Supports horizontal scaling and sharding across multiple servers.
• Flexible Querying: Supports complex queries and indexing

Installation of MongoDB on Ubuntu

1. Update package index:

   sudo aptupdate

2. Install MongoDB

3. Start MongoDB: Enable and start the MongoDB service:

   sudo systemctl enable mongod
   sudo systemctl start mongod

4. Check MongoDB Status: Verify that MongoDB is running:

   sudo systemctl status mongod

5. Access MongoDB Shell: Once MongoDB is running, you can access the MongoDB shell:

   mongo

These databases—MySQL, PostgreSQL, and MongoDB—are widely used for different types of applications:

• MySQL is ideal for structured data and high-performance relational applications.
• PostgreSQL is suited for complex, large-scale applications that require advanced data handling and extensibility.
• MongoDB is great for modern applications that handle large volumes of unstructured or semi-structured data.

Each database has its strengths and can be chosen based on the needs of your project. You now have a foundation for setting up these databases on Ubuntu and can start experimenting with them to build real-world applications.