Data dictionary

11.4.2.1 explain the purpose of data dictionary

Data dictionary

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, where the database is physically stored, 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

Data dictionary of table "Students_of_NIS".

Field Name Data Type Field Size for display Validation Description Example
studentID int 10

Type check,
the whole number

unique identifier of each user 4
student_firstname string 25 Length check, <=25 characters  first name of the user "Ranida"
student_surname string 25 Length check, <=25 characters  surname of student "Imasheva"
student_age int 2 Range check,
>= 12 AND <=19
age of user 16
resident_of_city boolean 5 True or False determines whether a student is a city resident  True

Questions:

1.Explain the term "Data dictionary".

2.Give the list what data dictionary describes.


Exercises:

Ex. 1

Quiz "Validation and Verification"

Ex. 2

A school plans to keep records of Sports Day events for different years in a database. The data that needs to be held for each event in a particular year in illustrated in following table Results:

EventID Year EventName Winner TimeOrDistance
GA100 2018 Girls Under 14 100m

Tanya Gordon

16.1
BJ100 2019 Junior Boys 100 m John Harris 13.1

Create Data dictionary for table Results

 


Exam questions:


 

Категория: Relational databases | Добавил: bzfar77 (10.11.2020)
Просмотров: 153 | Теги: database, data type, field size, field name, data dictionary | Рейтинг: 5.0/1
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