This textbook appeared as a reference database of SQL-EX.RU project. Therefore special attention is paid to the practice of use of language queries for manipulation of data – SQL DML.

However knowledge of only this sublanguage limits professional skills of the specialist. We are going to further develop the textbook at least in two directions:

• Language of definition of the structure of data – SQL DDL,
• Optimizing of queries.

Besides, it is planned to regularly update the content of the project, i.e. to reflect changes, taking place within SQL standard and in recent developments of top producers of database management systems.