What is a Database?
A relational database is a collection of
related tables.
A table is a kind of organised file where
data about a certain type is organised
into records (rows) and fields (columns).
Each field in a table constitute a property
of the data to be stored in the table.
Example 1: The Sample Bookstore
Database
• Books Table
(ISBN, TITLE, AUTHOR, YEAR, LISTPRICE,
PUBLISHERID)
• Publishers Table
(PUBLISHERID, PUBLISHERNAME,
ADDRESS, CITY, STATE, ZIPCODE, PHONE)
• Orders Table
(ORDERID, DATE, PUBLISHERID)
• Order Details Table
(ORDERID, ISBN, QUANTITY)
KEY
The key of a table is a combination of its
fields that uniquely identify each record in
that table. The underlined field(s) above
are the keys of the corresponding tables. .
Relationship Between Tables
• The relation between the tables may be either
one-to-many (1-M) or many-to-many (M-M).
• For instance, a publisher will most probably
publish more than one book. So, the relation
between the Publishers and Books tables ‘s 1-M.
On the other hand, there may be more than one
book in a specific order and a specific book may
be ordered several times, that is in several
orders. So, the relation between the Order
Details and Books tables is M-M.
Microsoft Access is software that enables us to create and
manage such databases. A Microsoft Access file has the
extension mdb (Microsoft data base).
•
When you start Microsoft Access, it will ask you if you want to create a new
database or open an existing database If you choose to open an existing
database, the database window will be displayed on the screen. The
database window has 7 objects:
1.
2.
7.
Tables (open an existing table for editing, design a table, create a table)
Queries (a query is a question about the database written in pre-defined
forms)
Forms (a form is a formatted window for managing data in a database)
Reports (a report is a formatted print-out that outputs information about
a database; a report may be based on a table or a query)
Pages
Macros (kind of computer program to be executed automatically one after
another; is used to automate repetitive tasks)
Modules (programming in Visual Basic for Applications)
•
Note that all objects are stored in a single Access file on disk.
3.
4.
5.
6.
Create a New DB
To open an existing database:
Select the Open option from the File Tab
Add a Table
You can add a new table to an existing
database by using the tools in the Tables
group on the Create tab.
A Table is displayed in one of two views:
• Design View: to define the table initially,
specify the fields it will contain or modify
the table definition
• Datasheet View: to add, edit or delete
records
Create a Table in Design View
Database Fields
For each field, you define:
•
•
Field Name (up to 64 characters including letters, numbers, space)
Data type
–
–
–
–
–
–
–
–
–
Number (digits, decimal point, plus or minus sign)
Text (up to 255 characters)
Memo (up to 64,000 characters)
Date/time
Currency
Yes/No (Boolean/Logical) or True/False
OLE (field created by another application)
AutoNumber (1,2, ... assigns the next number when you add a record)
Hyperlink (Web address-URL)
Design View
In the design view of a table the following
information on each field is displayed:
1.
2.
3.
Field Name
Data Type
Properties
Plus the primary field(s)is indicated by a key
before the field name.
PROPERTY
• A property is a characteristic or attribute of an
object that determines how the object looks and
behaves. Every access object (tables, forms,
queries, reports) has a set of properties.
Properties are displayed and/or changed in a
property sheet.
IMPORTANT NOTE:
• First select the field in design view whose
property you want to display.
The field properties displayed in the design view are:
•
•
•
•
•
•
•
•
•
•
Field Size (adjusts the size of a text field or limits the allowable
value in a number field)
Format (changes the way a field is displayed)
Input Mask (data validation: the data entered by the user must
match the input mask)
Caption (label other than the field name to be used in reports
and forms)
Default Value
Validation Rule (rejects data that does not conform to the
validation rule)
Validation Text (error message to be displayed when data
does not conform to the validation rule)
Required (must value)
Allow Zero Length (null text or memo fields)
Indexed (for efficient search purposes each table may be
indexed on various fields, e.g. surname; the table is indexed on the
primary key by default)
MODIFICATIONS ON A FIELD
• In order to add/delete a field in the design view
select (point to) the corresponding field(s), right
click and select add/delete rows as appropriate.
• In order to change the primary key, point to the
row where the new primary key field resides,
right click and select the primary key command.
• If the primary key is composed of more than one
field, select all the components by pressing the
Ctrl key upon selection and then issue the
Primary Key command.
Find and Replace Commands
• Home Tab; Find/Replace Command .
• If the Match Case check box is checked then ph is
different than PH.
• The search is performed over the specified field/table in
the Look In list box.
• In the Match list box, selecting Whole Field identifies
that Davis is different than Davison.
• The replacement may either be selective or automatic.
Selective replacement is a loop of find next and
replace/find next combination whereas automatic
replacement means clicking the replace all button.
FILTERING
A filter displays a subset of records from
the table according to a specified criteria.
The easiest way to implement a filter is:
• to click in any cell that contains the value
of the desired criterion.
• Then click the Filter by Selection button on
the Database toolbar.
Deleting a table from a database
Select its icon in the Tables Group of the
and press the Delete key.
Exiting Access
1.
2.
Close the table(s)
File Menu; Close
Exit Access
File Menu; Exit