Download Worksheets52-56

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Data Base: an introduction
What is a database
A database is a collection of logically related data designed to meet the information needs of one or more
users.
The term “database” in English is related to any archive of information, also in paper form: for example, the
cards for the different books in a library or an address book of clients are databases.
A database on a computer, therefore, is basically a file of data that represents a certain situation, a certain
organization or a given process and which contains sets of related information .
The use of files of data on a computer allows you to update and search through the information much more
easily than with a paper medium. We can think of a computer database as a filing cabinet where the
drawers are called tables, the cards are called records and the headings on the cards are called fields.
The data contained in the fields of a record (let’s take the example of a collection of books), can be of a
textual nature (text), like the author's name, the author's surname, the title of the book or the place of
publication, or numerical (numbers) like, for example, the number of pages.
Here is an example concerning how to organize your books in a table:
Fields
Record
Name
Surname
Title
Printed in
number
1
Number
date
of pages
Paola
Capriolo
Una di
Milano
236
2001
record
loro
TABLE
2
Alberto
Moravia
La noia
Roma
125
1976
3
Cesare
Pavese
La luna e i
Torino
177
1965
Falò
The advantages of storing data inside records instead of on paper sheets are numerous: for example, you
don’t need a cabinet and folders full of paper; but the main advantage is that on a computer the data can be
visualized and ordered according to your present needs, it is not necessary to prepare multiple files with an
index by author, by subject and so on; it is possible to order the data, do searches and quickly retrieve the
desired information even when using more than one search criteria (for example, not only all the books
printed in 2001 but all the books printed in 2001 that have more than 200 pages and that contain the word
"Sky" in the title).
The programs (applications) that allow you to create files of data, to update and modify them and to quickly
retrieve the desired information with many different search keys are called Data Base Management Systems
(DBMS). Access the program that will be used during this course, is a DBMS.
EuNIC-ENG
ITD-CNR/Centro Atene
Worksheet 52
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Microsoft Access: an
overview
What is MS Access?
Microsoft Access is a Database Management System or rather a specific program to create and manage
databases. It is included in the Office Suite, which also includes Word and Excel and uses the same graphic
interface.
The purpose of Access is to create and manage data files: with its commands you can create tables, forms
for the addition of data, you can order data inside the tables, you can rearrange and do searches on one or
more tables and print the whole content of tables or the results of your searches.
MS Access objects
In Access we have six different kinds of objects:
Objects
Functions
Tables
to store data
Queries
to ask questions of the data
Forms
input and display data easily
Reports
to show data contained in tables and queries in a suitable format
Macros
to automatize some repetitive operations that can be done on the data
Modules
to make particularly complex operations that you cannot manage with the macros
For the creation and management of a simple database only a small part of the functions and objects
available in Access is necessary. The fundamental functions are those needed to create a new table with
relative fields, to insert the data or to modify the existing data, to order them according to different criteria, to
do a search (query) of the data in relation to specific criteria.
EuNIC-ENG
ITD-CNR/Centro Atene
Worksheet 53
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MS Access: how to
create a table
Tables
A table is a data set relating to a specific subject (for example it can contain data about a collection of books,
about the products sold by a company, etc.).
A database is generally made of different related tables (for example, one table for the products sold, one for
the clients, one for the orders, etc.).
In any case, the table is the main element of a database.
The data in an Access table are divided into columns (fields) that correspond to a certain category of
information (for example, the fields "name", "telephone" or "address") and lines (records) that correspond to
the data set of a single element of the table (for example, the name, telephone and address of a specific
person).
How to create a new Table
When you open MS Access you see a table like this:
If you want to create a new database, in the New area of
the Task Panel choose Blank Database
MS Access asks you where do you want to save the new
database (the extension will be mdb)
Now you have three ways to create a new table:



Create a table in Design view, where you
can add fields, define how each field
appears or handles data, and create a
primary key.
Use the Table Wizard to choose the fields
for your table from a variety of predefined
tables such as business contacts,
household inventory, or medical records.
Enter data directly into a blank datasheet.
When you save the new datasheet,
Microsoft Access will analyze your data
and automatically assign the appropriate
data type and format for each field.
Here you can see a table created by
entering data directly.
Every field can have a different kind of
data such as text, numbers, dates, etc.
When you add your data the application
automatically recognizes the type of
data.
When you have saved the table, you
can open it and modify its structure at
any time.
EuNIC-ENG
ITD-CNR/Centro Atene
Worksheet 54
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MS Access: open a
table, filter and sort data
How to open an existing table
In the Database window, click on “Tables” under
Objects. Click the table that you want to open and
choose one of the following:
 Open the table in Design view, which shows the
design of the table. In Design view you can
modify the design of an existing table. To do
this, click “Design” on the Database window
toolbar.
 Open the table in Datasheet view, which
displays data in a row-and-column format. In
Datasheet view you can edit fields, add and
delete data and search for data. To do this, click
on “Open” on the Database window toolbar.
For example, with a double click on the “Employ” table you will see a datasheet like the one below.
Sort Ascending, Sort Descending
Sort the data in a table
Very often, when you work with data you
need to sort them.
To do this, first you have to select the
column that you want to sort, then you
have two possibilities:
 select “Sort Ascending” (or “Sort
Descending”) from the Records menu;
 click on the buttons as shown in the
picture.
How to filter data in a datasheet
Filter buttons
Filter By Selection and Filter By Form are
two different ways to filter records in a
form or a datasheet.
If you can easily find and select the value that you want the filtered records to contain, use “Filter By
Selection” in the Records, Filter menu. To filter by selection, select a field or a part of a field in a datasheet or
form, and then click “Filter By Selection”.
If you want to choose the values that you are searching for from a list, without scrolling through all the
records, or if you want to specify multiple criteria at once, use “Filter By Form” in Records Filter menu; it
displays the Filter by Form window, which is a blank version of the active form or datasheet, so you can filter
data.
EuNIC-ENG
ITD-CNR/Centro Atene
Worksheet 55
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MS ACCESS: queries
In addition to filter and sort data, you can also use a Query to extract records from a table.
What is a Query?
You use queries to view, change, and analyze data in different ways. You can also use them as a source of
records for forms, reports, and data access pages. There are several types of queries in Microsoft Access.
To create a query, first you have to know exactly what you need (for example you have a library and you
want to extract all the books printed in 2001); then you must define the criteria (in the example, the criteria in
the field "Year of edition" will be "=2001", or ">2000 And <2002") and finally save and run the query to
visualize the result.
How to create a Query
In the Database window, click on “Queries”
under Objects and do one of the following:
 create a query in Design view; in this way
you create a query by specifying the input
tables, field names, filters and sorting or
grouping properties;
 create a query by using wizard, in this way
the wizard asks you questions and creates
a query based on your answers.
To create a query you have to plan what you want to visualize and the criteria that you need. To get a better
idea of queries let’s look at the structure of a query that allows you to visualize all the books printed in 2001:
Table added
Query structure
Field selected
Table selected
Show or hide a field
Selection criteria
What you see in the previous form corresponds to a SQL (Structured Query Language) instruction. SQL is
the standard language that you use to query, update and manage relational databases such as MS Access.
From a conceptual point of view, to plan a query means that you have to turn a question into a series
of criteria that can answer your question.
EuNIC-ENG
ITD-CNR/Centro Atene
Worksheet 56