Database

Data dictionary

A data dictionary is simply a table that lists the fields of each table in a data model, together with the properties of each field. The data dictionary is important because this information can then be used to create a database for the data model using any chosen RDBMS

An example of a Data Dictionary is shown below:

Entity	Attribute	Key	Data Type	Format/Validation
DVD	DVD Code	Primary Key	Number (Integer)	Presence Check
	Film Code	Foreign Key	Number (Integer)	Presence Check/Restricted Choice
	Cost		Number (Integer)	Presence Check/ Currency/Range check >=1 and <=3
MEMBER	Member ID	Primary Key	Integer	Presence Check
	Title		Text	Presence Check/ Restricted Choice - Miss, Mrs, Mr, Other
	Forename		Text	Presence Check
	Surname		Text	Presence Check

Note the data type for Number is shown as an Integer.

The 3 main validation checks are:

• Presence - make sure data is entered
• Restricted Choice - gives a list to choose from
• Range - make sure data entered is within a given range

A quick and easy way to remember them is to remember the initial letters PRR (think aout purring like a cat!)

Click here to download exercises on creating data dictionary. Use the same layout as above and show each exercise to your teacher before moving on to the next one