Transcript What is a Database?

Databases
Standard Grade
What is a Database?
• A structured collection of similar information
that can be searched and sorted.
• A database is made up of files, records and
fields.
What is a Database?
• A database is an organised, structured collection of similar
information.
• A database can be stored on paper (manual) or on a computer
(electronic).
• A program that is used for organising data on a computer is called a database
package.
• Data is organised in a database as files, records and fields:
Files….Records…Fields?
Files
A file is a collection of records.
Data in a database is saved on the computer as a data file and contains data on a
particular topic
e.g. a Films data file.
Records
A record is a collection of fields.
A record is a collection of organised data on a particular person or item.
Fields
A field is a single item of information.
A field is part of a record that holds a particular piece of data e.g. Surname.
Sample Fields
Here is a sample record from a telephone directory data file made up of
different fields:
Field
Title
Mr.
Forename
John
Surname
Smith
Address
101
High Street
Record
Town
Ayr
Postcode
Tel. No.
KA7 3KL
01292
262626
What is a Database used for?
• Databases are used by many types of business and organisations such
as:
•Telephone Directory
• Police National Computer
• Inland Revenue
• Driver and Vehicle Licensing Centre
• A personal Christmas card list
• A mailing list
• Data held in a database can be shared between other computer packages
such as a word processor package – e.g. Mail Merge.
Advantages of an
electronic database?
• Information is immediately available.
• Records can be processed quickly.
• Records can be processed accurately.
All of this is impossible in a manual
system !!!!
Features of a Database?
• Databases have many of the features common to a general purpose
package.
• There are some special features of a
database:
• Create fields
• Add and alter records
• Search
• Sort
Create Fields
• The first step on setting up a database is deciding on the fields it requires.
• Fields hold the information you want to store.
• You can set the size and type of a field.
• Size: You can decide how many characters a field can hold e.g.
a Postcode field to hold KA18 3GH would require a minimum of 8 characters as
the space counts as a character!
• Type: Fields can hold different types of data:
• A text field holds letters.
• A number field holds only numbers.
• Date and time fields hold numbers formatted into date and time.
Add and Alter Records
• The next step is to enter records into the empty database. A new record has to
be created for each item. e.g.
Record 1
Mr
John
Smith
1 Anytown
Scotland
01929 393939
Mrs
Susan
Jones
5 The Town
Scotland
01521 447210
Record 2
Search Records
• You can run a search on a database for specific information.
• You can search on a field (or fields) based on certain conditions you require.
e.g. search for the forenames and surnames of people whose test mark was
greater than 50.
Sort Records
• Sorting allows you to organise records into a particular order:
• alphabetic
• numeric
• ascending (1,2,3,4,5…)
• descending (Z, Y, X, W …)
• The sort is done by choosing which field the database is to be sorted into
e.g. sort alphabetically by surname.
Additional features of a Database
Reports
• any information printed out from a database is a report.
• you can search for information, then sort it into an order,
and decide what fields you wish printed out in what order.
• this is known as a report definition.
Computed Fields
• A computed field (also called a calculated field) can be created in a
database or report.
• It carries out a calculation on a field or fields and returns an answer
(similar to a spreadsheet formula in a cell).
Example:
If a database has the fields <Total Pay> and <Total Deductions>, then a third
called <Net Pay> could be set up with the formula:
(=Total Pay – Total Deductions).
This is a computed field.
Altering Input/Output formats
• You can decide how the information in your database is presented by altering the
format.
• You can change the way the input screen looks and format a report for output.
• The position of fields can be rearranged and formatted into a particular order
and layout.
• This is useful for designing input screens and producing documents such
as invoices for output.
Keywords
Use of Keywords
• When searching for a particular record or part of it, the text that is used for the
search is called a keyword.
• It is also known as a search string.
• However, care must be taken that the correct keywords are used.