Data Types

When a database is designed, all the fields are set to accept a particular data type. This helps check for the wrong type of data being entered and makes sure the data is stored as efficiently as possible. It also means it will be sorted correctly.

Alphanumeric/text fields

A field of this data type will accept  text, numbers and symbols

Example include: Surname: Smith

Forename: Paul

Car Registration Number: B1234XY

Numeric fields

A field of this data type is used to store numbers. Number fields are used to store numbers because:

the data will be sorted correctly (i.e. the numerical data 2,3,20,30 would be sorted as 2,20,3,30 if it was stored in a text field)

There are two types of numeric field you need to know about:

  • Real - used for decimal numbers such as 3.4, 3.1427 and 6.0 etc. Real numbers can be formatted as currency (i.e. £5.67) or to a fixed number of decimal places (i.e. entering 3.1427 into a real number field formatted to two decimal places would mean it appeared as 3.14)
  • Integer - used for whole numbers.

Logical/Boolean fields

A field of this data type will only let you enter a 'Yes' or a 'No', Male or Female, On/Off.

Date/Time

A field of this type stores days, months and years and Time.

Example include 15 August 2001,

15-08-2001

10:15 PM

22:15

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