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Intro to Databases (using Microsoft Access)

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Title: 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 )

4
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.

5
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)
7
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

8
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.

9
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.

10
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.

11
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.

12
Relational DBMS Products
13
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

14
Clients and Servers
15
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.

16
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.

17
Other Types of Client And Server Programs
18
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

19
Web Browsing
  • TODO show architecture diagrams for
  • Web
  • Email
  • IM
  • File sharing

20
What is a network?
  • A network is a group of computers that can
    communicate with each other directly.

21
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
22
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
23
Clients and Servers
  • There are two general classifications of
    computers (AKA machines) on a network (or the
    Internet)
  • clients
  • servers

24
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.

25
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.

26
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
27
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".

28
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

29
Database Client Server Architecture
30
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

31
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
32
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).

33
Application Programs
34
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.

35
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.

36
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.

37
Structured Query Language (SQL)
38
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.

39
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.

40
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).

41
One Database Many Application Programs
42
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
43
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.

44
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

46
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.

47
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.

48
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.

49
Overview of Databases using Access 2007
50
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.

51
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)

52
Creating a new Access database
  • Start Access
  • and
  • Click Here

53
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

55
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.

57
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 )

58
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 Between Datasheet 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 table Step
    1 Click on the Home tab Step 2
  • Click on the arrow under the View button Step
    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

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
  • QUESTION Since 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
  • ANSWER In 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 larger Use 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
    question List the titles of all books that have
    more than 140 pages.

126
Opening the Query Designer
  • To create a query
  • Click the Query Design button 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-click here 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 Click in a column
139
Running A Query
140
Running A Query
  • Once youve added the tables and fields, you can
    start to see some results.
  • To see the results of the query
  • Click on the Run button from the Results
    group of the Design Tab. (see the results on
    next slide ) OR
  • Another way to do the same thing click on the
    Design View option from the View button.

141
Query Results (datasheet view)
  • The results (or the datasheet
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