Field

// ** Field ** // // ** (1) ** // A space allocated for a particular item of information. A tax form, for example, contains a number of fields: one for your name, one for your Social Security number, one for your income, and so on. In database systems, fields are the smallest units of information you can access In spreadsheets, fields are called //cells //

Most fields have certain [|attributes] associated with them. For example, some fields are numeric whereas others are textual, some are long, while others are short. In addition, every field has a name, called the // field name. //

In database management systems, a field can be // required, // // optional //, or// calculated. // A // required field // is one in which you must enter [|data], while an// optional field // is one you may leave blank. A calculated field is one whose value is derived from some [|formula] involving other fields. You do not enter data into a calculated field; the [|system] automatically determines the correct value.

A collection of fields is called a [|//record//].

Types of Data

Some of the most common types of data are:
 * Alphanumeric (numbers and text)
 * Numerical (digits and the decimal point)

> > All telephone numbers are entered as text, as the first zero does not meet the rules for a number. > (If you put a telephone number in as a number, the first zero disappears). > Key Field > >  In each table one of the fields is chosen as the key field (or primary key ). The key field is the unique identifier for a particular record. > For the database shown before, the key field is the field on the left called the Car_ID. > No two cars can have the same Car_ID number. > Key fields are chosen so that there can never be any doubt over which record you are referring to. > For a database of students, the key field could be the candidate number as these are unique. > > > >
 * Date (a set of numbers, e.g. 11/03/2007)
 * Boolean (true or false, yes or no)