Информатика / Computer science

SQL (Structured Query Language) is a standard language for accessing and manipulating databases.

Data Definition Language (DDL) is a family of computer languages ​​used in computer programs to describe the structure of databases.

Data Manipulation Language (DML) is a computer language including commands permitting users to manipulate data in a database.

The data dictionary contains data about the database. The data dictionary is very important because it contains information about what is in the database, who is allowed to access it, etc. Database users usually do not interact with the data dictionary, this is only available to database administrators.

The data dictionary describes: Contents, Format, Structure of a database, Relationship between its entities or objects

In the project work, the data dictionary is used at the design stage in order to determine the content of database tables: field name, the type of fields, the length of each field for display, validation to be used, a description of the field content, an example of the value.