# SQL (Structured Query Language) Introduction

In order to become familiar with SQL and SQL-based platforms, one have to gain basic knowledge about some of the basic concepts. Here I will list what seems to be to be important to know before jumping to learn any SQL-based platform. These concepts helps you to have a big picture about what you are about to learn and why you need to use them. Of course, I might change this list over the time as I myself gain more and more experienced in teaching SQL. For some the following concepts I have written a small description and for others I don't; anyway, this is to provide a checklist for your start point, not to provide you with extensive definitions. I'm sure you can find many comprehensive definitions using search engines and generative AI tools.

Important basic have-to-knows before learning SQL:

1. What are Database?
    
2. What is a Relational Database?
    
3. What is SQL (Structured Query Language)?
    
4. What are the most popular SQL-Based Databases?
    
    * MySQL:Fast and scalable, Commercial Open Source.
        
    * Oracle: Commercial, Enterprise-Scale.
        
    * MariaDB: Open Source.
        
    * PostgreSQL: Opensource.
        
    * Some other smaller projects like: SQLite, HSQL, ...
        
5. What does CRUD (Create, Read/Select, Update, Delete) mean?
    
    The four basic actions that one can do using databases are:
    
    * Creating/Inserting Data
        
    * Read/Select some Data
        
    * Update Data
        
    * Delete Data
        
6. In a Relational Database, what does a Database represent?
    
    It contains one or more tables.
    
7. In a Relational Database, what does a Relation/Tuple represent?
    
    It contains tuples and attributes.
    
8. In a Relational Database, what does a Tuple/Row represent?
    
    a set of fields which generally represent an "Object", like a person or a music track
    
9. In a Relational Database, what does an Attribute/Column/Field represent?
    
    One pf the possible many elements of data corresponding to the object represented by the row
    
    ![Image from https://en.wikipedia.org/wiki/Relational_database](https://cdn.hashnode.com/res/hashnode/image/upload/v1705998248205/1bc877f1-b873-417e-a20b-5a410198cd65.png align="center")
    
10. What is a Database Schema?
    
11. What is the SQL Architecture? How SQL commands are run on a SQL Server (regardless of what kind of SQL Client and/or Server you are using)?
    
    ![Picture from "Database Design and Basic SQL in PostgreSQL" coursera course>Week1>"SQL Architeture"](https://cdn.hashnode.com/res/hashnode/image/upload/v1705999167044/d618c7d2-97b5-4839-8fe9-2c4d8a45e4d9.png align="center")