Introduction to SQL

In this lesson, you will understand what is database, what is SQL and the relation between them.

What is Data?

In general, data means any kind of information. Data can be in the form of numbers, text, images, videos, series of bits (eg: 0010110101) and so on.

The main difference between data and information, is that information can be read normally by humans, while data is the form of information that can be read by softwares and machines or it's not have a meaning as it before manipulated.

Data is a plural world, the singular of if is Datum.

What is a Database?

A database is an organized collection of data that can be easily accessed and managed. data can be retrieved, edited, deleted and restored any time you want.

The symbol of a database is a cylinder, because it looks like a data container.

Importance of a Database

A database is the most important element in any project. Websites, games, and applications use databases to store their Data. For eg; user information like usernames, passwords, emails, articles etc.. are all stored in database.

The page that you are reading now, is stored in a database.

In general, a database let you:

  • Store information in a way that can be later easily accessed and managed.
  • Specify the type of each information will be saved whether it's TEXT, NUMBERS, DECIMAL, DATE etc..
  • Set conditions to specify wheter the value is accepted or not.
  • Create backups and restore data in case of any problems occurs.
  • Eliminating redundant data by applying normalization concepts.

What is SQL?

SQL is stands for Structure Query Language. It's a set of commands that can be used to manipulate and manage databases.

SQL commands are mainly categorized into five categories:

  • DDL – Data Definition Language
  • DQL – Data Query Language
  • DML – Data Manipulation Language
  • DCL – Data Control Language
  • TCL – Transaction Control Language

With our SQL tutorial you will learn all these commands and more in details.


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