Guide to Databases

This is a complete guide to databases, where you’ll learn the foundations and advanced concepts of the most widely used database technologies -

• SQL: The standard language to interact with relational databases.
• MySQL: A popular open-source database used in web applications and enterprises.
• PostgreSQL: An advanced open-source relational database known for reliability and performance.
• PL/SQL: Oracle’s procedural extension of SQL for writing powerful database programs.
• MongoDB: A NoSQL database that stores data in flexible, JSON-like documents.

Here, you’ll understand how each of these works, what they’re used for, and how they fit into real-world applications.

1. SQL

• SQL Tutorial
• SQL Interview Questions
• SQL Cheat Sheet
• SQL Exercises 

2. MySQL

• MySQL Tutorial
• MySQL Interview Questions

3. PostgreSQL

• PostgreSQL Tutorial
• PostgreSQL Cheat Sheet
• PostgreSQL Exercises

4. PL/SQL

• PL/SQL Tutorial
• PL/SQL Interview Questions and Answers

5. MongoDB

• MongoDB Tutorial
• Complete MongoDB Roadmap
• MongoDB Interview Questions with Answers 
• MongoDB Exercises