Intro to Databases (using Microsoft Access)

1
Intro to Databases (using Microsoft Access)

• Yitzchak Rosenthal

2
Database (DB)

• A Database is an organized collection of data
  that can be accessed and manipulated by computer
  programs.

3
People who use databases

• End Users
• Most business people do not usually use a
  database directly. Rather, business people use
  programs geared to their specific business needs.
  Behind the scenes those programs store or
  retrieve data from a database in response to the
  users actions.
• Technical IT Professionals (e.g. programmers,
  database administrators)
• IT Professional such as programmers and database
  administrators need to understand the in-depth
  issues about databases. These professionals
  create and maintain the programs that are used by
  the end users.
• Business Analysts (BA)
• When a new program needs to be created, the
  business analysts work with both the end users
  and the technical IT professionals to design
  the programs. The BAs dont actually create the
  programs, they just work on the design. BAs must
  also understand databases concepts.
• (See architecture diagram later in this
  presentation )

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Database (DB) vs. DataBase Management System
(DBMS)

• Database (DB)
• A Database contains the actual data.
• Database Management System (DBMS)
• A Database Management System (DBMS) is the
  software that is used to add, remove and manage
  the data in a database.
• Difference between DB and DBMS
• You can think of a database and a DBMS similar to
  the way you think about a word processing program
  (e.g. Microsoft Word) VS a word processing file.
  The DBMS is similar to the word processing
  program, while the database is similar to a word
  processing file.

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One DBMS can control many different databases

• A single Database Management System can control
  many different databases.
• Individual databases contain information about a
  particular topic.
• EXAMPLE A telephone company may have the
  following different databases (as well as many
  others). These different databases can all be
  controlled through one DBMS program
• Human Resources Database contains information
  about employee name, titles, hire dates,
  salaries, pension and benefit information, 401K
  data, etc
• Customer and billing database information
  about customer names and addresses, billing
  information, calling patterns, etc
• Assets database information about real estate
  that the company owns and leases, cell phone
  towers and leased lines, etc.
• Marketing database information about marketing
  campaigns, advertising rates, locations of
  billboards that are being used, times/stations
  and rates for radio and TV ad spots, data from
  focus groups, etc.
• etc.

6
Categories of Databases (relational, object
oriented, hierarchical, network)
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Relational / Hierarchical / Network / Object

• Databases are categorized by how they organize
  information.
• Types of databases
• Hierarchical Database model
• Network Database model
• Object Oriented Database model
• Relational Database model

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Hierarchical Databases

• Hierarchical Databases
• Data is organized into a hierarchy, similar to
  the folder/file hierarchy of the file system.
• Hierarchical databases can be faster than an
  equivalent relational database. However, with
  modern faster hardware this is not as much of an
  issue as it originally was.
• Hierarchical databases are not used much anymore
  for storing business data.
• IBMs IMS database is an example of a
  hierarchical database that is still used, mostly
  on large mainframe computers.

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Network Databases

• Network databases
• The word network in network database refers
  to how the information is organized in the
  database. (The word network is NOT related to
  the common concept of a computer network.)
• Network databases were proposed as an enhancement
  of the hierarchical database.
• Discussion of network databases is primarily
  academic since they are not really used anymore.

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Object Oriented Databases

• Object Oriented Databases
• Data is organized into information about
  objects.
• Object Oriented Databases are designed to be
  easily integrated with Object Oriented
  programming languages.
• Object oriented programming languages are very
  popular today. However, object oriented
  programming languages can ALSO be used with other
  types of databases. In practice most object
  oriented programs today use Relational Databases.
• Object Oriented databases are the newest type of
  database. They will probably NOT replace
  relational databases but their use will probably
  grow.
• An Object-Relational database is an object
  oriented database that can be implemented on top
  of a relational database.

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Relational Databases

• Relational Databases
• Data is organized into many tables of
  information.
• Vast majority of databases in use today are
  Relational databases.
• This is the type of database that we will be
  studying in depth.

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Relational DBMS Products
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Current Relational DBMS Products

• Most popular
• MySql open source DBMS. Can be downloaded and
  used for free. Powerful. Companies can purchase a
  technical support license from MySql, inc. Used
  a lot by smaller companies. Not as quick to catch
  on in larger fortune 500 companies.
• Microsoft SQL Server Microsofts high-end
  DBMS. More powerful than Access (i.e. faster, can
  handle more data, more users, better security
  features, etc).
• Microsoft Access Microsofts low-end DBMS.
  Used for smaller applications. Cheaper than SQL
  Server to buy/license.
• Oracle first commercially successful Relational
  DBMS. Very powerful. Has majority market share
  for large DB applications in fortune 500
  companies.
• Others
• Sybase
• IBM UDB
• IBM Informix
• many others

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Clients and Servers
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Client Programs and Server Programs

• Client programs and server programs are programs
  that are designed to communicate with each other.
• A client program makes requests of a server
  program to send some information or perform some
  action.
• The server program performs the requests of the
  client program and sends the client a response.
• The overall architecture of such a system is
  known as a client-server architecture.

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Example databases

• Example
• In the database architecture described above, the
  application program is acting as a client
  program and the DBMS is acting as a server
  program.
• The application program requests the DBMS to
  lookup some information in the database and the
  DBMS performs the lookup and returns the results
  to the application program.

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Other Types of Client And Server Programs
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Other types of client and server programs

• The client server model is used to implement many
  different types of computer applications.
• Examples
• Web browsing
• Email
• Instant Messaging (IM)
• Many other examples

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Web Browsing

• TODO show architecture diagrams for
• Web
• Email
• IM
• File sharing

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What is a network?

• A network is a group of computers that can
  communicate with each other directly.

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What is Internetworking?

• any network can communicate with any other
  network
• some communications are direct (e.g. A-B,
  A-C, C-D)
• some communications go through other networks
  (e.g. B-C, B-D, A-D)

Network A
Network B
servers
direct communication line
clients
Network C
Network D
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The Internet

• The Internet "cloud" in the diagram represents
  many many networks connected to each other.
• The internet permits communication (usually
  indirect) between any two computers attached to
  the internet.

Network A
Network B
servers

The Internet
clients
Network C
Network D
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Clients and Servers

• There are two general classifications of
  computers (AKA machines) on a network (or the
  Internet)
• clients
• servers

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What Is a Server?

• Server Machine
• a computer on a network that runs programs
  ("Server Programs") which provide other computers
  on the network (i.e. "Client Machines") with
  services.
• Server Program (AKA Server Software)
• these are the programs that are run on "server
  machines" to provide other computers on the
  network with services
• Server
• The term "server" is sometimes used to refer to a
  "server machine" and is sometimes used to refer
  to a "server program"
• In general it is the thing (machine or program)
  that provides the services. You will be able to
  tell from context the word refers to the machine
  or the program.

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What is a Client?

• Client Machine
• a computer on a network that communicates with a
  Server to get some services.
• Client Program (AKA Client Software)
• a program that runs on the "client machine" which
  communicates with the server to get some
  services.
• Client
• The term "client" is sometimes used to refer to
  the client machine and sometimes used to refer to
  the client program
• In general it is the thing (machine or program)
  that uses the services. You will be able to tell
  from context the word refers to the machine or
  the program.

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One server, many clients

• In general, one server handles the requests of
  many clients.
• If there are too many clients for a single server
  then you can usually add a second (third, fourth,
  etc) server to handle the extra load.

server
clients
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Server Types

• There are many many types of servers. The
  following are just a few
• Web Server Sends web pages to clients that
  request them. The client program that
  communicates with a web server is a web browser.
• Email server Delivers email from one client to
  another client
• IM server Coordinates IM connections
• File server Allows client machines to store
  files on the server machine's disk drives. (e.g.
  Z drive, F drive, etc)
• Print server Allows different machines to use a
  single printer.
• Network server This is a "traffic cop" that
  controls the communications that allow computers
  on the network to "talk" with each other.
• Database Server Coordinates access to the
  information in a database. Allows different
  client programs to read/write/modify information
  in the database.
• Custom Server For running a custom application.
  The custom application would also consist of
  custom client software. For example, a bank may
  develop an application so that its branches can
  exchange their financial information in "real
  time".

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One computer can run both client programs and
server programs at the same time

• A single computer can simultaneously run several
  server programs and client programs.
• Example
• a person sitting at the console of a database
  server can run a web browser that gets a web page
  from a different web server.
• In this case the "database server machine" is
  running a "web client program" (i.e. the
  browser).
• When referring to the database, this machine can
  be thought of as the server machine and when
  referring to the web, this machine can be thought
  of as the client machine.
• Another example
• The "database server program" might store a file
  on another machine.
• In this case the database server machine is
  acting as a client to the "file server machine"
• Many server programs on one machine
• You may have one machine that runs a database
  server program and a web server program

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Database Client Server Architecture
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Database Architecture Diagram

• The diagram on the next slide shows the
  organization of a typical database system. Dont
  be worried if you dont understand the diagram
  now. The diagram will be referenced and explained
  throughout the coming slides.
• Two computers in the diagram
• The computer on the left is running an
  application program (see later slides for an
  explanation)
• The computer on the right is running DBMS
  software (see later slides for an explination).
  The computer running the DBMS software is shown
  without a screen. This is because the user
  doesnt use this computer, rather the application
  program does. A computer that runs software that
  is used by other programs is known as a server
  computer. The program that it runs is known as a
  server program.
• Symbols in the diagram
• A cylinder is generally used to represent a hard
  drive or a database.
• See next slide

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Architecture Diagram
Application Program running on users computer
DBMS software running on server computer
(this is expressed using SQL, not English)
Step 2 Whats Joe Smiths tel?
Step 1
DB Management System (DBMS) Server Program
CLICK
Step 4 938-4763
Step 3 DBMS Software finds answer in database on
server computers hard drive.

EXPLINATION Step 1 User runs application program
on his computer. Step 2 application program
sends query to server Whats Joe Smiths tel
Number? (query is actaully expressed using
Sequential Query Language (SQL), NOT in English
as in picture)Step 3 DBMS Software looks up
answer in the database. Step 4 DBMS Software
sends answer back to appl. program Step 5 (not
shown) application program displays answer to
the user.
Server Computers Hard Drive
First Name Last Name Telephone Address
Oscar Grouch 9837232 123 Sesame St
Joe Smith 9384763 987 Main St
Bugs Bunny 8372364 1 Rabbit Hole
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About the Diagram DB and DBMS

• The diagram above shows two different computers,
  one the left and one on the right. (The reason
  why there are 2 computers will be explained a
  little later.) The computer on the left is known
  as the client computer and the one on the right
  is the server computer. (The terms client and
  server will also be explained later.)
• The DBMS is shown as a program that is running on
  the server computer (the computer on the right).
• The database appears on the diagram below the
  server computer (the computer on the right). The
  cylinder that surrounds the data on the diagram
  represents the server computers hard drive.
  (Even though the hard drive is usually inside
  the server computer, it is often shown on such
  diagrams separately).

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Application Programs
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Application Programs

• People do not usually use a DBMS program
  directly, rather people use an application
  program.
• The application program communicates with a DBMS
  program to store or retrieve data from a database
  in response to the users actions.
• Very often, the application program and the DBMS
  are running on different computers and
  communicate with each other using the computer
  network.Note that it is possible to have the
  application program and the DBMS on the same
  computer. However for large database applications
  used by businesses, the DBMS is usually on a
  different computer than the application program
  is running on.

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About the Diagram Application Program

• The diagram above shows an application program
  that is running on the computer on the left.
• In Step 1 on the diagram, the application
  program in the diagram presents a screen for the
  user to enter a name and click a button to lookup
  the persons telephone number.
• The arrows for Step 2 and Step 4 show the
  application program and the DBMS communicating
  over the computer network to get the desired
  telephone number. The user does not need to know
  that this part is happening.
• In Step 5 (not shown on the diagram) the
  application program displays the telephone
  number to the user. It appears to the user that
  the application program knows the telephone
  number. However, really, the application program
  just asked for this information from the database
  management system.

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Other Types of Database Clients

• The following are all systems that use a database
• ATM machine data is stored on the banks
  database. The data is accessible from any ATM
  machine.
• Point of Sale when you buy items in a
  supermarket and the cashier scans the item
  the scanner and the checkout system acts as a
  client to the database server. The database sends
  product and pricing information back to the
  checkout system to produce the bill. The database
  also updates its inventory records to reflect the
  fact that the items have been purchased.
• EZ-Pass when a car passes through an
  ez-pass toll booth, the information about the
  car is recorded in a database which is then used
  to generate billing information.
• eCommerce websites use a database to keep track
  of product descriptions, customer orders and
  shipping information
• etc.

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Structured Query Language (SQL)
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Structured Query Language (SQL)

• The application program uses a special computer
  language, called Structured Query Language (SQL),
  to communicate with the DBMS program.
• SQL is often pronounced as sequel
• Users of the application program do NOT need to
  understand SQL. It is the computer programmers
  who create application programs who must
  understand how to write SQL.

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SQL Inserts, Updates, Deletes, Queries,

• The most common types of SQL requests are
• Inserts Requests from the application program to
  add information to the database (DB).
• Deletes Requests from the application program to
  remove information from the DB.
• Updates Requests from the application program to
  modify some information that already exists in
  the DB.
• Queries Requests from the application program to
  retrieve specific information from the DB. The
  diagram above shows the application querying the
  DMBS for Joe Smiths telephone number. This is a
  simple query that returns a single piece of
  information. Queries can be much more complex and
  return a lot of information. An example of a
  more complex query might be find the list of
  names and telephone numbers for those people
  whose last name begins with S and whose
  telephone number is in the 917 area code.

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Complete Explanation of Architecture Diagram

• Complete Explanation of Architecture Diagram
• Step 1 The user runs an application program that
  allows him to look up peoples telephone numbers.
  The user types in a name to lookup and then
  clicks the Lookup button.
• Step 2 The application needs to get the
  information so the application program sends a
  query to the DBMS over the computer network to
  lookup the information in the database. This
  query is expressed using the SQL programming
  language.
• Step 3 The DBMS looks up the telephone number in
  the database.
• Step 4 The DBMS sends the information back to
  the client application program.
• Step 5 The application program displays the
  answer to the user (not shown in the diagram).

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One Database Many Application Programs
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Many Clients at the Same Time

• The diagram above only shows a single client
  computer.
• In reality it is more common for many different
  client computers running application programs to
  communicate with the DBMS at the same time.
• EXAMPLE Given a database that stores information
  about flights for an airline. An application
  program might be created for the ticketing agents
  to issue tickets to passengers. It is possible
  for many different ticketing agents to use the
  application program on their different computers
  at the same time.

Server running DBMS
Clients running application programs
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Different types of application programs.

• The information contained in a database can be
  used by different types of application programs
  simultaneously.
• Example A database that tracks information
  about planes and flights for an airline might be
  accessed by any of the following types of
  application programs
• A program used by ticketing agents to sell
  tickets for the flights
• A different program used by the airplane
  maintenance staff to determine which planes need
  to be maintained based on how many miles they
  have flown so far
• A third program used by the payroll department to
  calculate paychecks based on the number of hours
  and miles flown by the crew.
• Etc.

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Features of Databases
45
Database vs. Excel

• Many students wonder why a database is useful
  more than an Excel file would be for storing
  data.
• The following slide lists some features of modern
  databases that cannot be easily accomplished with
  a program such as Excel

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Features of Modern Databases

• Automated storage, retrieval and manipulation of
  the data - programs can access the data, not just
  people
• Network accessible. Data can be accessed over a
  network by several users/programs at the same
  time
• Able to process HUGE amounts of data generally,
  the amount of data that data database can process
  is limited only by the amount of disk space on
  the computer.
• Efficient (i.e. fast) storage, retrieval and
  manipulation of the data
• Flexible querying capability You can quickly
  summarize and reorganize the data in the database
  in many different ways.

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Features of Modern Databases (continued)

• Validation features. Has features for preventing
  bad data from being entered into the database
  (e.g. typos or illogical information such as a
  persons age being recorded as 237, or as a word
  such as blue, etc). Databases can be setup with
  rules to describe what is considered valid data.
  Invalid data will not be accepted into the
  database.
• Durable data. Modern databases have features to
  ensure that data will remain valid and
  uncorrupted even in the face of catastrophic
  errors such as a power outage.

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Features of Modern Databases (continued)

• Security. Authentication means that before
  accessing the data, a user must login or
  otherwise identify who they are. If a user has
  already logged into the operating system (e.g.
  windows) then many databases can identify the
  user based on how he logged into the operating
  system. Authentication is necessary to allow
  the DBMS to enforce security of the data. The
  database can be setup with rules to indicate
  which users can access which data. For example a
  database might store information about employees
  in a company. The names and telephone numbers
  might be available to every employee in the
  company. However, salary data might only be
  available to employees in the human resources
  department.

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Overview of Databases using Access 2007
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What is Microsoft Access?

• What is Microsoft Access?
• Access is a Database Management System (DBMS)
  program (see above for an explanation of what a
  DBMS is).
• Access contains features to allow designers of
  database applications to create and manage the
  database. This includes the ability to create
• Tables to store the data
• Queries that extract and display information
  from the tables
• Reports that display the information from a
  query in a fancy formatted way
• It is important to remember that even though
  Access provides the ability to run queries
  directly, often the queries are started by an
  application program, and not directly by a user.

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Books Database

• The information in this tutorial will be based on
  storing information in a database that keeps
  track of books.
• The database will store information about
• books (title, number of pages, retail price, etc)
• authors (names, addresses, etc)
• publishers (names addresses, etc)
• Advances and royalties (i.e. how much each author
  was paid)

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Creating a new Access database

• Start Access
• and
• Click Here

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Name the Database File

• Specify a name for the database file here.
• If you need to choose a different folder, click
  here.
• Click Create

54
Extension .accdb vs .mdb

• Extension
• The extension for an Access 2007 file is .accdb
• The extension for files from Access 2003 and
  earlier is .mdb

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Access Files and Viruses
56
Opening a File That You Didnt Create

• It is possible for a malicious person to insert a
  computer virus into an Access Database file.
  (NOTE This is also true for other Microsoft
  Office applications, e.g. word files, powerpoint
  files, excel files, etc.)
• Therefore, if you open an Access file that you
  didnt create yourself, you must trust the person
  or website who you got the file from.
• Access can tell which files were created on the
  computer that you are using. If you open an
  Access file that was created on any other
  computer, you may see a warning message (see next
  slide).
• The message does NOT mean that the file contains
  a virus. Rather it means that any file that was
  created on another computer is suspect and that
  you must trust the person or website that you got
  the file from.

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Security Warning Message

• If you open an Access file that was created on a
  different computer you may see the warning
  message shown below.
• Click on the Options button to see options
  (see next slide )

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Enable this content

• Click on the Options button to get this
  dialog box.
• If you trust the person you got the file from
  (e.g. a book publisher, your professor, etc.)
  then choose Enable this content and press OK.
• If you dont choose to Enable this content then
  you will still be able to use the access file,
  but some of its features may not be available to
  you.

59
Tables
60
What is a database Table

• Information in a relational database is organized
  into several tables
• Each table stores information about a specific
  type of concept or thing (known as an entity).
  Examples people, cars, books, purchases, etc.
• Below is an example of a table that contains
  information about books. Each row in the table
  stores information about a specific book.

61
Parts of a table

• Every table has
• A name of the table
• Rows (or Records) that contain the data for
  specific items (or entities)
• Columns (or fields) that contain specific
  attributes of each item.
• Each column (or field) has a name.
• See next slide

62
Example Books table
Name of the table
Columns or fields of the table. Each column
contains information about a different
attribute of a book.
A row (or record) of the table (contains info
about a specific book)
Column names or field names
The value of one field in a specific row.
To add a new row just start typing in the last
row of the table (the one with the next to it)
63
Entering new Information

• To enter a new row of information start typing
  the new information on the last row of the table
  (the row with the next to it).
• Press TAB and Shift-TAB to move from one field to
  the next.
• When you start typing the new row will have a
  pencil icon next to it. The pencil means that the
  row is not yet saved to the database. Once youve
  entered all of the fields and press TAB, the row
  is AUTOMATICALLY SAVED in the database and the
  pencil icon goes away. You do not have to do
  anything else to save the new row.

64
Deleting a Row

• Deleting a Row
• STEP 1 right click on the header to the left
  of the row
• STEP 2 choose Delete Record

65
Creating Your First Table
66
Every database must have at least one table

• Every database must have at least one table
• Therefore, when you create a new database, Access
  automatically presents the following screen which
  allows you to create a new table.
• See next slide

67
Creating Your First Table

• The table already has a single field named ID.
  This is a special field that will be important
  for later.
• The ID field has numbers that are automatically
  assigned by the database as new rows are added.
  We will discuss this more later.
• To enter information just start typing HERE (see
  next slide). This will automatically create new
  fields.

68
Adding a New Row

• Our first table will store information about
  books (titles, number of pages, prices,
  publication dates)
• To enter information about the first book,
• start by typing the title (The Great Pickle
  Caper) into Field1.
• Press TAB to move to the next field and enter the
  number of pages (87).
• Continue pressing TAB to enter the price (9.99)
  and publication date (1/1/2007).
• To move to the next field, press the TAB key (or
  Shift-TAB to move to the previous field).
• To enter information about the next book, (not
  shown in picture)
• click on the 2nd row and enter the title, etc.

Then press TAB and type this.
Click here and type this
The number 1 is automatically entered here by
Access
Click here to enter info about the 2nd book.
Click and drag here to make field wider or
narrower.
69
Saving and Naming the Table

• To save the table click on the save icon (or
  if you close the table youll be asked to save
  it).
• When you save the table, you will be asked to
  give a name to the table.
• The navigation pane lists the names of all
  created tables. If your database contains more
  than one table, you can double click on a table
  name to see the contents of that table.

70
Switching BetweenDatasheet View and Design
View
71
Design of a table

• In addition to the data in a table, you must
  specify the Design of each table.
• The Design defines the type of data that is
  allowed in each field.
• You cannot see both the design and the data at
  the same time. The data is visible in the
  Datasheet View of the table and the design is
  visible in the Design View of the table.
• To switch between the Datasheet View and
  Design View of the table, use the View button
  as shown on the following slides

72
Design View

• To see the Design View of the tableStep
  1Click on the Home tabStep 2
• Click on the arrow under the View buttonStep
  3
• Choose Design View

Currently looking at the Data. Follow the steps
at the left to view the Design
73
Datasheet View

• To see the Datasheet View of the table
• Step 1 Click on the Design or Home tabs
• Step 2 Click on the arrow under the View
  button
• Step 3 Choose Datasheet View

Currently looking at the Design. Follow the
steps at the left to view the Data
74
Design View
75
Design of a table

• The design of a table describes
• The names of the columns (or fields).
• The type of information you may place in each
  field.
• The type of information allowed in a field could
  be any of the following. (These types will be
  explained more fully in later slides)
• text,
• number,
• currency,
• auto-number,
• date/time,
• yes/no,
• and some other types.
• It is IMPOSSIBLE to enter information into a
  field of a different type than the type that is
  defined for that field.
• Example pages in the books table is defined to
  only accept number data (see next slide).
• Therefore page numbers must be entered as numbers
  (e.g. 298).
• It will be IMPOSSIBLE for someone to enter words
  for the page number field (e.g. yellow).
• It is also IMPOSSIBLE to enter words that
  represent numbers such as two hundred and ninety
  eight.
• See next slide for the design of the books
  table

76
Design View

• Design view allows you to specify the field
  names and data types of each column in the table.
  

• Description describes in English what the
  column is used for. The Description is ignored by
  Access.
• The section on the bottom gives more control over
  the type of data allowed in the currently
  selected field on top.

77
Data Types
78
Data Types

• Below are some of the data types that can be
  defined for fields.
• Keep reading for more info

Data Type Whats allowed in the field Examples
Number Only numbers 0 -3 325 12.345
Text Anything that can be typed on the keyboard Hello there!redseveral words in a row
Currency Numbers that will be used to represent currency amounts 125.99
Date/time A date and/or a time. 1/1/2008 600 AM 1/1/2008 600 AM
Yes / no Yes or no. These values are represented on the screen as a checked checkbox (Yes) or an empty checkbox (No). Yes No
Autonumber (See description on a later slide )
79
Data Types - Number and Text
80
Number Data Type

• NUMBER
• Can store only numbers
• Cannot store letters or any special symbols
  (e.g. _at__)
• Use the number data type to store numerical data
  such as peoples ages, number of pages in a book,
  etc.
• Integer numbers vs. numbers with decimal points
• By default, you can only store integer values
  (i.e. whole numbers) in a number field
• You can modify number fields to allow the storage
  of numbers with decimal points but we will not
  show how to do this here.

81
Text data type

• TEXT
• Can store any combination of letters, numbers and
  special symbols (e.g. _at__)
• Use the Text data type for fields that will store
  peoples names, addresses, names of colors, etc.

82
Storing numbers in a Text field - Question

• QUESTIONSince both the Number and Text data
  types can be used to store a number, how should a
  field that is intended to store a number (eg.
  number of pages, zip codes, tel. numbers, etc) be
  defined, with the Number data type or Text data
  type?
• ANSWER see next slide

83
Storing numbers in a Text field - Answer

• ANSWERIn general, it is best to use the
  Number data type for numbers that you may need
  to either - perform mathematical calculations
  with, OR - compare two values numerically to see
  which is largerUse the Text data type for all
  other numbers
• There are exceptions to this rule, but dont
  worry about them.
• EXAMPLES on next slide

84
Storing numbers in a Text field - Examples

• EXAMPLES
• Number of pages in a book should be stored as
  Number. This is because you may want to add up
  all the pages from several books - e.g. add up
  the page counts from all Harry Potter books to
  see how prolific JK Rowling is (performing
  mathematical calculations). You may also want to
  compare two different books to see which has more
  pages (numerical comparison)
• ZIP Codes and Telephone Numbers should be stored
  as Text. This is because you would never need to
  do math with these values and you generally
  wouldnt need to compare two ZIP codes or
  telephone numbers to see which is numerically
  larger.

85
Other Data Types
86
Currency Data Type

• CURRENCY
• Can store numbers that represent amounts of money
  (e.g. prices, bank account balances, etc.)
• Numbers are automatically displayed with a
  and 2 decimal places of information

87
Date/Time Data Type

• Date/Time
• Can store a date, a time, or both a date and a
  time (i.e. a moment in history)
• Works similar to the way Excel stores dates and
  times.

88
Yes/No Data Type

• Yes/No
• Can ONLY store the word Yes and the word No.
• Use Yes/No to store information that can only
  have one of two values.
• Works similarly to the way Excel stores
  Logical/Boolean values.

89
Autonumber Data Type

• Autonumber
• Used to store a number that is different for
  every row in the table.
• The actual numbers to be put in the table are
  automatically generated by Access.
• By default, the number for the first row in the
  table is 1.
• Every time a new row is created the value in the
  autonumber field is one more than it was for the
  last row.
• Autonumber is generally only used for primary
  key fields (see later in the presentation for
  information about what a primary key field is
  and more information about the Autonumber data
  type.)
• You may only have one Autonumber field per table.

90
Relating 2 Different Tables in a 1 to Many
Relationship
91
Adding Publisher Information

• We would like to add the publishers name,
  address and tel for each book.
• There is a RIGHT way to do this and
• There is a WRONG way to do this.
• See next slides for more info

92
The WRONG Way to Do It

• The WRONG way to add publisher data would be to
  simply add columns to the existing books table,
  such as below.
• This approach is WRONG because it introduces
  duplicate information into the database.

New columns for publisher information
Duplicated information for Abc Publishing
Duplicated information for Doe Books
93
Duplicate Information is BAD

• One of the goals of a relational database is to
  never repeat the same information twice in the
  database (or at least to minimize duplications as
  much as possible).
• Well see how it is possible to do that soon
• Two reasons to avoid duplicate data
• (more important) Duplicate data can lead to
  errors. Suppose that the tel. number for Doe
  Books were entered differently in two different
  places. You would not know which number is
  correct. Even if you knew that the tel. number
  was correct in one part of the database you would
  have to check EVERY row to make sure that it is
  correct all over. It is much easier to have a
  single copy of the data that you can check.
• (less important) To save disk space.

94
The RIGHT Way to Do It

• The RIGHT way to do this is to create a separate
  table for publishers.
• You will then need to somehow connect the two
  tables to show which book was published by which
  publisher.
• More info on next few slides

95
What is a Primary Key field?

• What is a Primary Key field?
• A Primary Key is a field (or set of fields) that
  is guaranteed to not be empty and to have a
  different value for every single row in a table.
• We need to add a Primary key to the Publishers
  Table.

96
The Publishers Table (with a primary key)

• Below we show a new table named Publishers.
• The publishers table now contains a column named
  pubId that contains a different value for every
  row in the table. This column will serve as a
  primary key for the publishers table.
• We will soon see how we make use of the primary
  key

97
Relating the Books table to the Publishers table

• To record the publisher for each book, we can add
  a column to the Books table to record the pubId
  of the publisher of the book.
• The two tables are shown below.
• The pubId column in the books table is known as a
  foreign key.

98
Primary Key VS Foreign Key

• Primary Key
• Must have different values for each row in the
  table
• The primary key is used to uniquely identify each
  row in the table
• A table may only have ONE Primary Key
• Foreign Key
• Values may be the same for different rows of the
  table
• A foreign key stores a value from the primary key
  of a different table.
• A table may have more than one foreign key (well
  see why later)

99
Names of Primary and Foreign key fields

• As mentioned above, each Foreign Key field in one
  table, has a corresponding Primary Key field in a
  different table.
• A foreign key field in the first table often has
  the same name as its corresponding primary key
  field in the second table.
• However, these names can be different too.

100
Entity Relationship Diagram (ERD)

• We show the relationship between tables in a
  database using an Entity Relationship Diagram.
• The diagram below shows that the Books and
  Publishers tables are related to each other
  through the primary key foreign key
  relationship of the pubId fields in each table
  (the line is drawn from pubId to pubId).
• The key symbol next to pubId in the publishers
  table indicates that pubId is a primary key in
  the publishers table.
• The 1 and the infinity sign (a sideways 8) will
  be discussed on the next slide

101
One To Many Relationship

• One to many relationship
• A book can only be published by one publisher.
• However, a publisher can publish many books.
• This defines a one to many relationship.
• The 1 in the ERD represents the one side of the
  relationship (i.e. one publisher) and the
  infinity sign represents the many side of the
  relationship (i.e. can publish many books)

102
Review how to store a 1 to Many relationship in
a database

• How to create a 1 to many relationship in a
  database
• Create 2 different tables, one for the 1 side and
  one for the many side
• Create a primary key for the table on the 1 side
• Create a foreign key for the table on the many
  side. This foreign key will be used to store
  values from the primary key of the other table.

103
Another 1 to Many Relationship (authors-Books)
104
Authors and Books

• Next we want to record which author wrote which
  books.
• As a first attempt we will approach this just
  like we did for publishers.
• We will create a different table to store author
  information (name, address, tel , etc).
• The authors table will have a primary key
  (authorId).
• We will add a new column to the books table to
  store the authorId. This will be a foreign key.
• See the next slide

105
Tables
New authors table
Primary Key
Added a new foreign key field to the books
table.
106
Who Wrote Which Book?

• From the previous slide, you can see that
• Joe Jones wrote
• How to Stuff an Olive
• Waltzing with Walt and Wendy
• Uncle Sam is Sleeping
• Alice Aames wrote
• The Great Pickle Caper
• A is for Artichoke
• Sue Smith didnt write any books

107
Updated ERD

• The updated Entity Relationship Diagram is below.
• This ERD shows that
• a book can only have one author (we will change
  this soon, keep reading )
• However an author can write many books

108
Many-Many Relationships (Authors-Books)
109
Many-Many relationships

• In the real world
• A single book can be written by many authors and
• A single author can also write many books
• This is an example of a many-many relationship.

110
Allowing Several Authors For a Single Book

• Unfortunately, the way the database is currently
  setup, we cannot record information about books
  that were written by more than one author.
• For example, suppose that both Alice Aames and
  Sue Smith collaborated to write the book A is
  for Artichoke. There is no way to record that in
  our database.
• NOTE You cant add another authorId in the books
  table for A is Artichoke since there is only
  one authorId value allowed.

111
Recording a Many-Many relationship requires 3
tables.

• The proper way to record information about
  many-many relationships in a database is to use 3
  tables.
• We will modify our database tables to allow us to
  record information about books that were written
  by several authors.
• Keep reading

112
Authors_Books Table

• We create a new table called Authors_Books that
  shows which author wrote which book.
• We do not need to record the name of the author
  in this table, just the authors ID.
• Similarly, we do not need to record the title
  of the book, just an ID for the book. To create
  an ID for the books table we will add a new
  column, bookID and make it the primary key of the
  books table.
• Keep reading

113
Creating the new tables

• On the next slide you can see the new table
  structure.
• The data in the new tables on the next slide
  represents the exact same information that we had
  in the previous table structure, i.e. the same
  authors wrote the same books (this slide doesnt
  show yet two authors for a single book).
• On a later slide we will show that you can now
  add a 2nd author for one or more of the books.

114
Tables
New primary key for books table
Removed authorId field from books table and moved
it to the authors_books table
New table authors_books shows who wrote which
book.
Authors table is the same as before
115
Recording 2 authors for one book

• Each row in the Authors_Books table represents
  the fact that a specific author was involved with
  writing a specific book.
• With the new table structure you can indicate
  that 2 authors wrote the same book by just adding
  another record to the Authors_Books table for the
  2nd author.
• To indicate that Alice Aames and Sue Smith
  collaborated to write the book A is for
  Artichoke add the row as shown on the next slide.

116
Tables
Added this new row. Everything else is the same
as before.
These two rows now show that both Alice Aames and
Sue Smith collaborated to write A is for
Artichoke.
117
Composite Primary Key and 2 Foreign Keys of
Authors_Books Table

• Foreign Keys
• The authorId column in the Authors_Books table is
  a foreign key that stores the value of a primary
  key from the authors table.
• The bookId column in the Authors_Books table is a
  foreign key that stores the value of a primary
  key from the books table.
• Composite Primary Key
• The primary key in the Authors_Books table is
  made up of both the authorId and the bookId
  fields together.
• A primary key that is made up of more than one
  field is known as a composite primary key
• What this means is that there cannot be two rows
  in the Authors_Books table that have the same
  value for both the authorId and the bookId.
  However, two rows MAY have the same value for
  either the authorId or bookId.

118
Updated ERD for New Table Structure
119
Review of Major Ideas
120
Major Concepts

• Relational databases avoid the repeating of
  duplicate information.
• Different tables are created to store related
  types of information.
• Relationships between rows in the tables is
  implemented through primary-key to foreign-key
  relationships
• A one-to-many relationship can be represented
  with exactly 2 tables
• A many-to-many relationship must be represented
  using 3 tables
• An entity relationship diagram (ERD) shows the
  tables and how they are related to each other

121
Access Queries
122
What is a Query

• What is a Query
• A query means a question. We can ask the
  database a question about the data and the
  database will figure out the answer.
• Example on next slide

123
Example

• Example
• We can ask the database to list the titles of
  all books that have more than 140 pages.
• After you create and run the query (see later
  slides) the database would respond as shown
  below.
• To get the answer though, you must first
  understand how to ask the question (i.e. how to
  create the query) Keep reading

124
Creating a Query - Step 1 OpenING the query
design window
125
Example Query

• We will create a query that answers the following
  questionList the titles of all books that have
  more than 140 pages.

126
Opening the Query Designer

• To create a query
• Click the Query Designbutton on the Create
  tab.

127
Creating a Query Step 2 Specifying tables and
Fields
128
Choose the Table(s)

• When you open the query designer you are prompted
  to specify the tables that are needed to answer
  the query.
• To add a table to the query designer click on the
  table name and then click the Add button.
• (DO NOT choose a table if it is not necessary to
  answer the query).

129
Layout of Query Designer Window

• Top of Query window shows tables.
• Bottom shows other info about query (well
  explain more about this soon )

130
Adding more tables
Right Click here

• To add additional tables to the query
• Right click on a blank portion of the top of the
  query window and choose Show Table
• Then you will see the Show Table dialog box
  (not shown in picture) which allows you to add
  more tables.

131
Related Tables in a Query
Line that connects foreign key in books table to
primary key in publishers table.

• All tables that are in a query should be
  related to each other through a Primary Key
  Foreign Key relationship.
• If the primary key and the foreign key have the
  same name, Access automatically draws the
  connecting line that shows the relationship.
• If the primary key and the foreign key have
  different names, Access doesnt draw the line
  automatically.

132
Drawing missing relationship lines
Then drag to here and let go of mouse button
Click here

• To manually draw a relationship-line
• click on the foreign key in one table
• Drag it over the corresponding primary key in the
  other table
• Let go of the mouse button.
• (you can also drag in the reverse direction)
• NOTE lines that you draw manually may not be
  labeled with the 1 and the infinity sign.

drag
133
Deleting Relationship Lines

• To remove a relationship line that was drawn
  incorrectly
• Right click in the middle of the line
• Choose Delete

Right-click here and choose Delete
134
Removing a table from the query
Right-click here and choose Remove Table

• You can remove a table from a query.
• This does not remove the table from the database
  (i.e. your data will still be there) it just
  removes the table from participating in
  answering the query.
• To remove a table from the query
• Right click on the name of the table and then
• Choose Remove Table

135
Tables and lines must be correct

• A query should never include more tables than
  necessary. If too few or too many tables are
  included in the query the results will not be
  correct.
• The relationship lines between the tables in the
  query must be drawn correctly or else the results
  of the query will not be correct.

136
Back to the example

• List the titles of all books that have more than
  140 pages.
• To answer our query, the database only needs to
  look at the contents of books table since the
  books table contains both the title and the
  number of pages for each book.

137
Bottom of query window
Double-clickhere and here

• The bottom of the query window lists the fields
  that will be involved in the query.
• Double click on each filed that is needed to
  answer the query.
• The fields are then listed in the bottom of the
  query window.

Fields are shown here and here
138
Adding and Removing Fields From Query

• To add or remove a column from the bottom portion
  of the query designer, click in one of the
  columns and press the appropriate button from the
  Query Setup group on the Design tab.
• Choose Delete Columns to delete a column
• Choose Insert Columns to insert a new column
• NOTE inserting or deleting columns from the
  query does NOT affect the underlying tables
  only the query.

Then choose appropriate button above
First Cl