SQL is a programming language for manipulating databases. Discover everything you need to know about it: how it works, use cases, learning methods…
It allows to store, manipulate and retrieve these data. It is also possible to perform queries, to update data, to reorganize them, or to create and modify the schema and structure of a database system and to control access to its data.
The history of SQL
The history of SQL began in 1969, when IBM researcher Edgar F. Codd defined the relational database model. This model is based on the association of “keys” with various data. For example, a username can be associated with a real name and a telephone number.
A few years later, IBM created a language for relational database management systems based on the work of Codd. This language was first called SEQUEL, for “Structured English Query Language”. After several implementations and revisions, it was finally called SQL.
Testing began in 1978, cand then IBM began to develop commercial products such as SQL/DS in 1981 and DB2 in 1983. Other vendors will follow, such as Sybase, Ingres, or Oracle which launched its first product in 1979
How does SQL work?
Applications can be programmed with different languages like Python, PHP or Ruby. However, historically, databases do not understand these languages. Until recently, they only understood SQL (although things have changed a lot in the last few years).
That’s why learning SQL is essential for working in the fields of application development or web development. Before being able to use it, it is necessary to learn its “markup”.
This is true for all programming languages. However, SQL has a unique characteristic that distinguishes it from other languages : the concept of tables.
Indeed, a database is made of tables. Each of these tables is composed of columns and rows, and represents a set of data. Therefore, SQL allows you to create or manipulate tables.
Several SQL commands are frequently used to work with databases. For example, “CREATE DATABASE” is used to create a database, “CREATE TABLE” is used to create tables.
The “SELECT” command allows you to find or extract data from a database. “UPDATE” allows you to adjust or edit data, and “DELETE” allows you to delete some data.
These are just a few examples of very commonly used commands, to give you an overview of how SQL works. The more complex the database, the more commands the user will need to use.
These commands are used to write “queries” to manipulate the data in the databases. The system interprets and processes these commands, for example to create a new record in a database.
What is SQL used for ?
SQL is used in all areas where databases are used. In other words, it can be found in almost any field where data is generated and analyzed.
In the finance industry, banking and payment processing applications store data about financial transactions and users. These systems are built on complex databases and require the use of SQL.
Similarly, music streaming applications such as Spotify or Deezer make intensive use of databases, for example to store the vast catalogs of music files from different albums by different artists.
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SQL is used to manipulate this data to find what the user is looking for, or to store data about the user and their preferences.
Social networks such as Facebook or Instagram use SQL to store a user’s profile information such as their bio or geographic location. Every time a user creates a post or shares content, SQL updates the database.
As you can see, the SQL language is used by a wide variety of applications that everyone uses every day. Most of the most popular software relies heavily on SQL.
What are the most popular SQL database systems ?
A database system is a program that allows a developer to work with a database through a user interface. This allows databases to be manipulated in a more intuitive way, especially through pre-designed templates and building tools.
These different tools simplify the life of the database programmer by automating the most common tasks such as cleaning the system. There are many of them.
The most popular worldwide is Oracle Database. This SQL database system is used in a wide range of industries, including data warehousing and online transaction processing.
Another popular system is MySQL, which is offered as open source and free of charge for individuals and companies. Small businesses and startups especially like it because it is free, and many open source applications also use it.
For its Windows operating system, Microsoft offers its own SQL database management system called SQL Server. This system is used in consumer software and on web servers running on Windows, which gives it a large user base.
Finally, PostgreSQL is MySQL’s main competitor. It is another open source database system, used by many startups because it is free. This system is compatible with all major OS such as macOS, Windows and Linux. Unlike other systems such as SQL Server, PostgreSQL makes a point of following the standard SQL syntax which makes it much easier to learn.
How do I learn SQL ?
There are a variety of options for learning SQL. You can turn to dedicated books to learn the basics and discover the mistakes you should not make. There are also many online courses, such as those offered by DataScientest.
If you encounter a problem or difficulty while learning or using SQL, you can also turn to online communities for help and expertise. You can find support from experienced programmers on platforms like Stack Overflow, Quora, Reddit or StackExchange.
It only takes a few weeks to learn the basics of SQL if you already have some programming skills and know other languages. The best way to accelerate your learning is to work on real projects : a database, a web application… practice every day, and you will progress quickly.
You now know everything about SQL. To learn more, discover our file on database management or our Data Engineer training.