3497302 Ms Access and Database Fundamentals

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MS Access and Database




Monday, May 30, 2011 © 2008. Content - Anurag | Stylised - Ananda 2

Index

� Introduction to MS Access and Database

� Hierarchy used in Access

� Opening/Creating an Existing Database

� Creating Tables in Database

� Defining Relationships

� Creation of report

� Creating a Form

� Difference between File processing & DBMS� Characteristics of DBMS

� Types of end users

� Advantages of using DBMS

� Data Models & Schemas

� Categories of Data Models

� Definition of entity, attribute and relation

� DBMS architecture

� Data independence





Introduction

Access is a database program that enables one can store information such

as a client list, products, invoices, inventory, events, and other collections of data.

In addition to entering the data in a database table, you have several tools for working

with the data. Forms for simpler data entry can be created. You can create a query to

display a set of record. All these elements are Access objects and are stored together in the database.

Microsoft Access is a powerful program to create and manage your databases.

In Access terms, a database is a collection of all the tables, queries, forms,

data access pages, reports, macros, and modules that compose a complete system.

Relational refers to the fact that the tables that comprise the database relateto one another.





Hierarchy that Microsoft Access uses in breaking down a database

� Database File

This is your main file that encompasses the entire database and that is saved to your hard-drive or floppydisk.

Example StudentDatabase.mdb

� Table

A table is a collection of data about a specific topic. There can be multiple tables in a database.

Example #1) Students

Example #2) Teachers

� Field

Fields are the different categories within a Table. Tables usually contain multiple fields.

Example #1) Student LastNameExample #2) Student FirstName

� Datatypes

Datatypes are the properties of each field. A field only has 1 datatype.

Database File

Table

Field

Datatype

Value





Opening/Creating an Existing Database

� After starting Access, create a new database or open an existing database.A database is stored as a file on your computer or on a network computer.

To work with the objects in a database, one must open the database file.To open an existing database , follow these steps:

When Microsoft Access first starts up, a dialog box is automatically displayed with options to create a new

database or open an existing one. If this dialog box is displayed, click Access Database Wizards, pages, and

projects and then click OK.

On the Databases tab, double-click the icon for the kind of database you want to create.

Specify a name and location for the database.

Click Create to start defining your new database





Creating Tables in Database

A table is a collection of data about a specific topic, such as students or contacts. Using a separate table for

each topic means that you store that data only once, which makes your database more efficient, and reduces

data-entry errors. Tables organize data into columns (called fields) and rows (called records).

� Primary Key

One or more fields (columns) whose value or values uniquely identify each record in a table. A primary key

does not allow Null values and must always have a unique value. A primary key is used to relate a table to

foreign keys in other tables.

For Example., make the Soc Sec # field the primary key, meaning that every student has a social securitynumber and no 2 are the same. To do this, simply select the Soc Sec # field and select the primary key

button





Defining Relationships

After setting up multiple tables in your Microsoft Access database, we need a way of telling Access how to

bring that information back together again. The first step in this process is to define relationships between

your tables. After this, one can create queries, forms, and reports to display information from several tables at

once.

A relationship works by matching data in key fields - usually a field with the same name in both tables. In

most cases, these matching fields are the primary key from one table, which provides a unique identifier for

each record, and a foreign key in the other table. For example, teachers can be associated with the students

they're responsible for by creating a relationship between the teacher's table and the student's table using the

Teacher ID fields.





Steps for defining references

In the database window view, at the top, click on Tools ---> Relationships

Select the Tables you want to link together, by clicking on them and selecting the Add Button

Drag the primary key of the Parent table (Teacher in this case), and drop it into the same field in the Child

table (Student in this case)

Select Enforce Referential Integrity

When the Cascade Update Related Fields check box is set, changing a primary key value in the primary

table automatically updates the matching value in all related records.

When the Cascade Delete Related Records check box is set, deleting a record in the primary table deletes

any related records in the related table

Click Create and Save the Relationship





Creating a Form

� It is a good idea to create a form using the wizard, unless you are an advanced user andknow what you are doing. Microsoft Access does a very good job of creating a form using

the wizard. The following steps are needed to create a basic form:

Switch to the Database W indow. You can do this by pressing F11 on the keyboard.

Click on the Forms button under Objects on the left side of screen

Double click on Create Form Using Wizard

On the next screen select the fields you want to view on your form.Click Next

Select the layout you wish

Click Next

Select the style you desire. Click Next

Give you form a name, and select Open the Form and enter information

Select Finish

You should see your form. To adjust the design of your form, simply hit the design button (same as with the

tables), and adjust your form accordingly





Creating a Report

� A report is an effective way to present your data in a printed format. Because you havecontrol over the size and appearance of everything on a report, you can display the

information the way you want to see it. If forms are for input, then reports are for output.Anything you plan to print deserves a report, whether it is a list of names and addresses, a

financial summary for a period, or a set of mailing labels. Again the Access Wizards walk

you through the process of defining reports.

Switch to the Database W indow. You can do this by pressing F11 on the keyboard.

Click on the Reports button under Objects on the left side of screen

Double click on Create Report Using Wizard

On the next screen select the fields you want to view on your form. Most of the time you would select all of them.

Click Next

Select if you would like to group your files. Keep repeating this step for as many groupings as you would like.

Click Next

Select the layout and the paper orientation you desire. Click Next

Select the style you desire..Click Next

Give you report a name, and select Preview the Report

Select Finish





Difference between File processing & DBMS

A number of characteristics distinguish the database approach from the traditional approach of programming

with files. In traditional file processing, each user defines and implements the files needed for a specific

application as part of programming the application. For example, one user, the grade reporting office, may

keep a file on students and their grades. Programs to print a student¶s transcript and to enter new grades into

the file are implemented. A second user, the accounting office, may keep track of students¶ fees and their payments. Although both users are interested in data about students, each user maintains separate files²

and programs to manipulate these files²because each requires some data not available from the other

user¶s files. This redundancy in defining and storing data results in wasted storage space and in redundant

efforts to maintain common data up-to-date. In the database approach, a single repository of data is

maintained that is defined once and then is accessed by various users. The main characteristics of the

database approach versus the file-processing approach are the following.





Characteristics of DBMS

� Self-Describing Nature of a Database System-

A fundamental characteristic of the database approach is that the database system contains not only thedatabase itself but also a complete definition or description of the database structure and constraints. This

definition is stored in the system catalog, which contains information such as the structure of each file, the

type and storage format of each data item, and various constraints on the data. The information stored in thecatalog is called meta-data, and it describes the structure of the primary database. The catalog is used by the

DBMS software and also by database users who need information about the database structure. A general

purpose DBMS software package is not written for a specific database application, and hence it must refer to

the catalog to know the structure of the files in a specific database, such as the type and format of data it will

access. The DBMS software must work equally well with any number of database applications²for example,

a university database, a banking database, or a company database²as long as the database definition isstored in the catalog.

� Insulation between Programs & Data and Data Abstraction

In traditional file processing, the structure of data files is embedded in the access programs, so any changes

to the structure of a file may require changing all programs that access this file. By contrast, DBMS access

programs do not require such changes in most cases. The structure of data files is stored in the DBMS

catalog separately from the access programs. We call this property program-data independence. In object-oriented and object-relational databases, users can define operations on data as part of the database

definitions. An operation (also called a function) is specified in two parts. The interface (or signature) of an

operation includes the operation name and the data types of its arguments. The implementation (or method)of the operation is specified separately and can be changed without affecting the interface. User application

programs can operate on the data by invoking these operations through their names and arguments,

regardless of how the operations are implemented. This may be termed program-operation independence.

The characteristic that allows program-data independence and program-operation independence is calleddata abstraction.





Characteristics of DBMS

� Support of Multiple Views of the Data

A database typically has many users, each of whom may require a different perspective or view of thedatabase. A view may be a subset of the database or it may contain virtual data that is derived from the

database files but is not explicitly stored. Some users may not need to be aware of whether the data they

refer to is stored or derived. A multi-user DBMS whose users have a variety of applications must providefacilities for defining multiple views.

� Sharing of Data and Multi user Transaction Processing

A multi user DBMS, as its name implies, must allow multiple users to access the database at the same time.

This is essential if data for multiple applications is to be integrated and maintained in a single database.

TheDBMS must include concurrency control software to ensure that several users trying to update the same data

do so in a controlled manner so that the result of the updates is correct. For example, when several

reservation clerks try to assign a seat on an airline flight, the DBMS should ensure that each seat can be

accessed by only one clerk at a time for assignment to a passenger. These types of applications are

generally called on-line transaction processing (OLTP) applications.





Types of end users

� End users are the people whose jobs require access to the database for querying,updating, and generating reports; the database primarily exists for their use.

There are several categories of end users:

Casual end users - occasionally access the database, but they may need different information each time.

They use a sophisticated database query language to specify their requests and are typically middle- or high-

level managers or other occasional browsers.

Naive or parametric end users make up a sizable portion of database end users. Their main job function

revolves around constantly querying and updating the database, using standard types of queries andupdates²called canned transactions²that have been carefully programmed and tested. The tasks that such

users perform are varied:

Bank tellers check account balances and post withdrawals and deposits.

Reservation clerks for airlines, hotels, and car rental companies check availability for a given

request and make reservations.

Sophisticated end users - include engineers, sc ientists, business analysts, and others who thoroughly

familiarize themselves with the facilities of the DBMS so as to implement their applications to meet their complex requirements.

Stand-alone users - maintain personal databases by using ready-made program packages that provide

easy-to-use menu- or graphics-based interfaces. An example is the user of a tax package that stores avariety of personal financial data for tax purposes.





Advantages of using DBMS

� Controlling Redundancy

In traditional software development utilizing file processing, every user group maintains its own files for handling its data-processing applications. For example, consider the UNIVERSITY database; here, two

groups of users might be the course registration personnel and the accounting office. In the traditional

approach, each group independently keeps files on students. The accounting office also keeps data onregistration and related billing information, whereas the registration office keeps track of student courses and

grades. Much of the data is stored twice: once in the files of each user group. Additional user groups may

further duplicate some or all of the same data in their own files. This redundancy in storing the same data

multiple times leads to several problems. First, there is the need to perform a single logical update²such as

entering data on a new student²multiple times: once for each file where student data is recorded. This leads

to duplication of effort. Second, storage space is wasted when the same data is stored repeatedly, and thisproblem may be serious for large databases. Third, files that represent the same data may become

inconsistent. This may happen because an update is applied to some of the files but not to others.

� Restricting Unauthorized Access-

When multiple users share a database, it is likely that some users will not be authorized to access all

information in the database. For example, financial data is often considered confidential, and hence onlyauthorized persons are allowed to access such data. In addition, some users may be permitted only to

retrieve data, whereas others are allowed both to retrieve and to update. Hence, the type of access

operation²retrieval or update²must also be controlled. Typically, users or user groups are given accountnumbers protected by passwords, which they can use to gain access to the database. A DBMS should

provide a security and authorization subsystem, which the DBA uses to create accounts and to specify

account restrictions. The DBMS should then enforce these restrictions automatically. Notice that we can

apply similar controls to the DBMS software.





Data Models & Schemas

One fundamental characteristic of the database approach is that it provides some level of data abstraction by

hiding details of data storage that are not needed by most database users. A data model is a collection of

concepts that can be used to describe the structure of a database and provides the necessary means to

achieve this abstraction. By structure of a database we mean the data types, relationships, and constraints

that should hold on the data. Most data models also include a set of basic operations for specifying retrievalsand updates on the database. In addition to the basic operations provided by the data model, it is becoming

more common to include concepts in the data model to specify the dynamic aspect or behavior of a database

application. This allows the database designer to specify a set of valid user-defined operations that are

allowed on the database objects.





Categories of Data Models

� Many data models have been proposed, and we can categorize them according to thetypes of concepts they use to describe the database structure.

High-level or conceptual data models- provide concepts that are close to the way many users perceive data.

Low-level or physical data models- provide concepts that describe the details of how data is stored in the

computer.

� Concepts provided by low-level data models are generally meant for computer specialists,

not for typical end users. Between these two extremes is a class of representational (or

implementation) data models, which provide concepts that may be understood by endusers but that are not too far removed from the way data is organized within the computer.Representational data models hide some details of data storage but can be implemented

on a computer system in a direct way.





Definition of entity, attribute and relation

An entity represents a real-world object or concept, such as an employee or a project, that is described in

the database.

An attribute represents some property of interest that further describes an entity, such as the employee¶sname or salary.

A relationship among two or more entities represents an interaction among the entities; for example, a

works-on relationship between an employee and a project





DBMS Architecture

� Three important characteristics of the database approach, are

Insulation of programs and data (program-data and program-operation independence);

Support of multiple user views; and

Use of a catalog to store the database description (schema). In this section we specify an architecture for

database systems, called the

� The three-schema architecture, which was proposed to help achieve and visualize these

characteristics.





Levels of DBMS

� The Internal or Physical Level

The collection of files permanently stored on secondary storage devices is known as the physical database.

The physical or internal level is the one closest to physical storage, and it provides a low-level description of

the physical database, and an interface between the operating system's file system and the record structures

used in higher levels of abstraction. It is at this level that record types and methods of storage are defined, aswell as how stored fields are represented, what physical sequence the stored records are in, and what other

physical structures exist.





Levels of DBMS

� The Conceptual Level

The conceptual level presents a logical view of the entire database as a unified whole, which allows you tobring all the data in the database together and see it in a consistent manner. The first stage in the design of a

database is to define the conceptual view, and a DBMS provides a data definition language for this purpose.

It is the conceptual level that allows a DBMS to provide data independence. The data definition languageused to create the conceptual level must not specify any physical storage considerations that should be

handled by the physical level. It should not provide any storage or access details, but should define the

information content only.





Levels of DBMS

� The External or View Level

The external or view level provides a window on the conceptual view which allows the user to see only thedata of interest to them. The user can be either an application program or an end user. Any number of

external schema can be defined and they can overlap each other. Because they have responsibilities for the

design and maintenance for the design and maintenance of the database, they at times need to be able tosee the entire database. The external and the conceptual view are functionally equivalent for these two users.





Data Independence

� The three-schema architecture can be used to explain the concept of data independence,which can be defined as the capacity to change the schema at one level of a database

system without having to change the schema at the next higher level. 2 types of dataindependence:

Logical data independence is the capacity to change the conceptual schema without having to change

external schemas or application programs. We may change the conceptual schema to expand the database,

or to reduce the database. In the latter case, external schemas that refer only to the remaining data should

not be affected. Only the view definition and the mappings need be changed in a DBMS that supports logicaldata independence. Application programs that reference the external schema constructs must work as

before, after the conceptual schema undergoes a logical reorganization. Changes to constraints can be

applied also to the conceptual schema without affecting the external schemas or application programs.

Physical data independence is the capacity to change the internal schema without having to change theconceptual (or external) schemas. Changes to the internal schema may be needed because some physical

files had to be reorganized²for example, by creating additional access structures²to improve the

performance of retrieval or update. If the same data as before remains in the database, we should not haveto change the conceptual schema. For example, providing an access path to improve retrieval of SEC TION

records by Semester and Year should not require a query such as "list all sections offered in fall 1998" to be

changed, although the query would be executed more efficiently by the DBMS by utilizing the new accesspath.



Thank you

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3497302 Ms Access and Database Fundamentals