Download Year 9 Databases DATABASES WHAT IS A DATABASE? A

Year 9 Databases
DATABASES
WHAT IS A DATABASE?
A database is an organised collection of information (or data) on a particular subject
(books, customers, products etc). Putting information into a computer database gives
you far more flexibility in arranging, displaying and printing that information. A
database is organised to make retrieving specific information easy.
The parts of a database:
Files: Think of a box of filing cards like those sometimes used in libraries. A
computers equivalent of the complete box is a file. A collection of related data; for
example, a student file would contain details of all students in a school.
Records: Within the library card box are the individual cards, each of which contains
information about one book. In a computer database, the cards are known as records
and most databases will display one record on the screen at a time, just as if you were
browsing through the cards in a card box. A set of related information about a thing
or individual.
Title: The Tempest
Title: William
The Tempest
Author:
Title: William
The Tempest
Author:
Shakespeare
Author: William
Shakespeare
Publisher:
Shakespeare
Publisher:
Cambridge
Publisher:
Cambridge
Cambridge
A file
One record
Fields:
Fields
Title:
Author:
Publisher:
Many records
Title:
The Tempest
Author: William Shakespeare
Publisher: Cambridge
The Tempest
William Shakespeare
Cambridge
On each card will be a number of different items of information: a library card might
list the title, author, and publisher. Each item of information on the computer
record is known as a field, and it consists of two parts: the field name and the field
data. The field names are Title Author or Publisher. They are the same on each
record and indicate what the field data represents.
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Year 9 Databases
Microsoft Access Database Manager:
Access is a software application used to create and manage a computerized database.
In Access, a data base consists of the following objects:
FORMS
Input data
to Tables
TABLES
Contain data
QUERIES
Ask
questions
about a table
REPORTS
Provide specific
data in a printed
(or onscreen)
format
 A table is a database object that stores data in rows (records) and columns
(fields). The data is usually about a particular subject, such as employees or sales.
CREATING A NEW DATABASE




Select Microsoft Access
Select Blank Database
In the File name box, type the name of your database.
Select Create
CREATING A TABLE
 Select Create table in Design view.
 Complete field name, data type, and field size.
To save a Table:
 Select File from the Main Menu
 Select Close
 Write the name of the table.
 Select O.K
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Year 9 Databases
VALIDATION:
Validation is the process of detecting any data that is, incomplete or unreasonable. A
computer can be programmed to validate the data entered; if the data supplied is
invalid the program can display a message on screen asking for a correct data entry.
To validate fields in an existing TABLE:


Select the table
Click Design





Click on the field to validate
Click on validation rule in field properties
Complete the validation rule, you may go to the expression builder by clicking on
Click on validation text
Complete the error
message for an invalid
entry
HOW TO DEFINE A PRIMARY KEY:
A primary key is a field that uniquely identifies each record.
HOW TO CREATE A LOOKUP FIELD (combo box):
There are 2 ways to do this:
1) Using an additional table
 Create an additional table containing the possible values (E.g.: in the school’s
database the House field values would be Fleming, Dodds, Brown or Monteith).
 In the Design View of the Main table, for the field that uses the combo box
(e.g.: House), the Data Type must be Lookup Wizard….
 Follow the steps of the wizard
 Choose the 1st option to look up the values in the additional table
2) Create the list of values directly in the wizard
 In the Design View of the Main table, for the field that uses the combo box
(eg: House), the Data Type must be Lookup Wizard….
 Follow the steps of the wizard
Choose the 2nd option to type in the values that you want
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Year 9 Databases
HOW TO CREATE A FORM
In this way you can see all the fields of a table arranged more like the printed
tracking sheet than like a spreadsheet.
 Click the Forms button in the left menu
 Choose the Create form by using wizard
 Complete the dialogue box.
HOW TO MAKE A QUERY
A query is used every time you want to interrogate or search a database or table.





Select the QUERIES button in the left menu
Select the table or tables you wish to interrogate and click Add.
Select Close.
Complete the table below in the following boxes: Field, Sort, Show & Criteria.
Select Query / Run or
How to specify different criteria for a query:

The value in a field is equal to a specific value: Example: The following query will return
the records for the Author “Charles Dickens”
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Year 9 Databases

The value in a field starts with a set value: Example: Books whose Title start with
C.
C*

The value in a field falls within a range of values (only numeric fields):
Complete the criteria for Books edited between the years 1930 and 1950.
Use the sort option to display
the data in ascending order.
Between 1930 and 1950
 The value in a field may be from a list of values:
Complete the criteria for Books that are “novel” or “short stories”.
Novel or short stories

Variable criteria:
Complete the criteria for Books that are a specific genre set when the Query is run.
[Input Genre:]
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Year 9 Databases
HOW TO MAKE A REPORT
With a Report you have greater flexibility to present summary information. You can include
totals. It is important to group and sort information. Create Reports using the wizard and
read carefully each step.
HOW TO INSERT A PICTURE IN A DATABASE



Add a field name Picture and define it as OLE Object
Open the Table and in the column picture click the right button of the mouse
Select Insert /Object
HOW TO STRETCH A PICTURE IN A FORM OR REPORT:
 Open the design view of the form or report
 Click the right button of the mouse where the picture should appear
 Select Properties
Change the size mode from clip to stretch
HOW TO ADD A HEADER & FOOTER IN A FORM:





Open the design view of the form
Drag the Detail Tab down from the Form Header thus creating a space for the header.
Select the Toolbox Label icon Aa and place it on the Form Header
Type in the title and format it as you like.
Apply the same steps for the footer.
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Year 9 Databases
Ways to perform calculations in a query
There are many types of calculations you can perform in a query. For example, you can
calculate the sum or average of the values in one field, multiply the values in two
fields, or calculate the date three months from the current date.
To display the results of a calculation in a field, you can use a predefined calculation
that Microsoft Access provides or custom calculations you define.
Use the predefined calculations, called "totals," if you want to compute the following
amounts for groups of records or for all the records combined: sum, average, count,
minimum, maximum, standard deviation, or variance. You choose one totals calculation
for each field you want to calculate.
Example: Calculations on all records:
To do this open Exercise 1 (Software packages). Create a new query in design view for the
table software packages.
1. Click the Totals icon on the toolbar.
2. The Total
row in the
design grid is
displayed.
3. For the field or fields you
want to group on, leave Group
By in the Total cell.
4
5
For the field you want to calculate, Type add it to the next column and in the Totals
row select the function count.
Run the query, your output should be as follows:
Type
Desktop Publishing
Graphics
Word Processing
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CountOfType
2
2
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Year 9 Databases
Using a calculated field:
For custom calculations, you need to create a new calculated field directly in the design grid.
You create a calculated field by entering an expression into an empty Field cell in the query
design grid.
Steps To create a calculated field:
1. In the design grid you give the calculated field a name followed by a
colon.
2. You click on the expression builder icon.
3. In the expression builder you build the formula necessary to
calculate the value for the desired field:
Double-click the Tables folder in the left
panel, it expands to show the tables in
the database Select a table, the fields
appear in the middle panel, a double click
on a field will paste it with an identifier
indicating the source of the field.
To calculate the value in stock for each product of the Software packages create a calculated
field in a query where the value is obtained multiplying price by stock.
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Year 9 Databases
WHAT IS A RELATIONAL DATABASE?
A Relational Database is a Database that consists of several files, which are
connected, in some way. For instance, in a video library there could be three:
 A Video file, to hold details of the videos kept, such as video title, actors,
duration.
 A Member file to hold all the members’ details such as name, address.
 A Rental file to hold all the details of the rentals, such as video number, member’s
number and date borrowed)
All three files (or databases) are related, but you need at least one common field in
all three files to be able to work satisfactorily. A relational database
management system (RDMS) is a program that enables you to organize data
stored in tables in a database.
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