One of the most important parts of a database is its data dictionary. The Data dictionary is a read-only set of tables that provides information about the database. A data dictionary is a table providing a comprehensive description of each field in the database. This commonly includes: field name, data type, data format, field size, description and example. This is shown in the example below.
|Field name||Data type||Data format||Field size||Description||Example|
|UserId||Number||6||Six digit number||601539|
|FirstName||Text||20||Employee first name||Jason|
|DOB||Date||DD/MM/YYYY||10||Date of birth as a short date format||15/09/2000|
|HourlyPayRate||Currency||#####.##||8||Rate of pay in dollars per hour||24.50|
|Height||Real||#.##||3||Height in metres, with two decimal places||1.58|
|FeesPaid||Boolean||1||Y or N for Yes or No||Y|
- field name: the name of the field as it appears in the database.
- data type: includes text, number, date, currency, yes/no (boolean).
- data format: any special formatting applied to the field; e.g. number of decimal places in number fields, short, medium and long date and time formats.
- field size: the number of characters allowed for a given field.
- description: a simple description of field contents.
- example: a typical field entry.
The data dictionary is structured in tables and views, just like other database data. All the data dictionary tables and views for a given database are stored in that database’s
A data dictionary is an important tool for all users, from end users to application designers and database administrators.