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Parts of a database

Database basics

A database is essentially a computerized record-keeping system.

Each unit of information you create is called a record and each record is made up of a collection of fields. Typically, a single record consists of a set of field names like: Title, FirstName, Surname, JobTitle, TelNo and ID. You fill in a form with the relevant information for each field to add a new record to the database. There are different data types.

§ Text - holds letters and numbers not used in calculations

§ Number - can only hold numbers used in calculations and reports

§ Memo - can store long texts

§ Date/Time - a date or time or combination of both

§ AutoNumber - assigns a number to each record

§ OLE Object - (object linking and embedding) holds sounds and pictures

§ Yes/No - for alternative values like true/false, yes/no, on/off, etc.

§ Hyperlink - adds a link to a website

Once you have added data to a set of records, indexes must be created to help the database fim specific records and sort (classify) records faster. An index performs the same function as in the back of a book or in a library. For example, if you regularly search your database by surname, the index should be defined on this field.

Relational databases

Two database files can be related or joined as long as they hold a piece of data in common. A file of employee names, for example, could include a field called 'DEPARTMENT NUMBER' and another file, containing details of the department itself, could include the same field. This common field can then be used to link the two files together.

Extracting information from a database is known as performing a query. For example, if you want to know all customers that spend more than Ј9,000 per month, the program will search the name field and the money field simultaneously.

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