Introduction to SQL

SQL is a structured query language that is used as an efficient way to store data, search for its parts, update, extract from the database, and delete.

Access to relational DBMS is made possible thanks to SQL. All major manipulations with databases are performed with it, some of them:

Extract data from a database
Insert records into the database
Update records in the database
Delete records from the database
Create new databases
Create new tables in the database
Create stored procedures in the database
Create views in the database
Set permissions for tables, procedures, and views

SQL dialects (SQL extensions)

SQL is a universal language for all relational database management systems, but many DBMS make changes to the language they use, thus deviating from the standard. Such languages are called dialects or extensions of the language.

Here are some of them:

T-SQL - Microsoft SQL Server dialect
PL/SQL - Oracle Database dialect
PL/pgSQL - PostgreSQL dialect

Which dialect to learn?

If you know that you need to learn SQL, you should learn standard SQL. However, if you already know which specific database you will be working with, it is probably best to learn its SQL dialect and just know that different databases may use slightly different syntax.

In our course, we offer you a choice between MySQL DBMS and PostgreSQL DBMS, as the 2 most popular solutions. You can switch between them at any time using one of the following methods:

select DBMS on the profile settings page
select DBMS in the code editor interface