This educational and practical guide represents the first, basic part of the training course on the SQL language offered by the Russian company PostgresProfessional. The training material is presented based on the use of the PostgreSQL database management system. The manual can be used both under the guidance of a teacher and for independent study of the SQL language. The manual is intended for students studying in the areas of 03/09/01 - “Informatics and Computer Science”, 03/09/02 – “Information Systems and Technologies”, 03/09. 03 – “Applied Informatics”, 03/09/04 – “Software Engineering” and 03/02/03 – “Mathematical support and administration of information systems”. It may be useful to a wide range of students and professionals who want to familiarize themselves with the basics of the SQL language in the environment of the PostgreSQL database management system.