Structures and linksField types

Depending on the information stored, the field type chosen to store it is very important.

Text field

• Stores words, numbers and other characters such as punctuation marks. Think of a text message in a mobile phone: this is similar to a string variable.
• Your address, your forename, your postcode and email address are all examples of Text Fields.

Number field

• Stores both whole numbers and decimal numbers. This is similar to a single/real/integer variable.
• Your height 1.62m (number field - real), the number of marks in your exam (62/100 number field - integer), and the number of days you have been absent from school (number field - integer)are all number fields.

Date field

• These store dates. A dentist’s database would keep track of all patients' details. If you are due a check-up, a date field would store when that is.
• Date of birth, the date of exams and events in a mobile phone calendar all use date fields.

Time field

• A time field stores a specific time.
• In a police report, the exact time when an incident took place would use a time field. Any important appointments and meetings would all use a time field to store start and finish times.

Graphic field

• A graphic field stores pictures and images. A picture on the school database, a profile picture on Facebook, and an image of a product on eBay would all be stored in a graphic field.

Calculated field

• This could have a type such as Number or Text, but the database works out what to put in there using a formula usually based on the contents of other fields in the record.
• For example, weekly wages may be calculated by multiplying an hourly pay rate by the number of hours worked.
• The percentage of attendance at school, age, and weekly wages would all be calculated fields.