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Database Management Database Management SystemsSystems

Chapter 1

Introduction

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Goal: Build a Business Application

Tools:Database DesignSQL (queries)Programming

Des

ign

SQ

L

Pro

gram

Des

ign

SQ

L

Pro

gram

Best:

Worst:

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DBMS: Database Management System

DatabaseA collection of data stored in a standardized format,

designed to be shared by multiple users.

Database Management SystemSoftware that defines a database, stores the data, supports

a query language, produces reports, and creates data entry screens.

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Drawbacks of old File methods

Uncontrolled DuplicationWastes spaceHard to update all files

Inconsistent data Inflexibility

Hard to change dataHard to change programs

Limited data sharing Poor enforcement of standards Poor programmer productivity Excessive program maintenance

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Advantages of Database Approach

Minimal data redundancy. Data consistency. Integration of data. Sharing of data. Enforcement of standards. Ease of application development. Data independence.

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Database Management Approach Data is most important

Data defined firstStandard format

Access through DBMSQueries, Reports, FormsApplication Programs3GL Interface

Data independenceChange data definition

without changing codeAlter code without

changing dataMove/split data without

changing code

All Data

DBMS

Program1 Program2QueriesReports

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Modifying Data with DBMS

Add cell number to employee tableOpen table definitionAdd data element If desired, modify reports

Use report writerNo programming

Existing reports, queries, code will all run as before with no changes.

Field Name Data Type Description

EmployeeID Number Autonumber..TaxpayerID Text Federal IDLastName TextFirstName Text . . . Phone Text . . .

CellPhone Text Cellular . . .

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DBMS Components Database engine

StorageRetrievalUpdate

Query Processor Data dictionary Utilities Security

Report writer Forms generator (input

screens) Application generator Communications 3GL Interface

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DBMS Engine, Security, Utilities

DataTables

DatabaseEngine

ProductItemID Description887 Dog food946 Cat food

OrderOrderID ODate9874 3-3-979888 3-9-97

CustomerCustomerID Name1195 Jones2355 Rojas

ProductItemID Integer, UniqueDescription Text, 100 char

CustomerCustomerID Integer, UniqueName Text, 50 char

SecurityUser IdentificationAccess Rights

Utilities

Concurrency andLock Manager

Backup andRecovery

Administration

DataDictionary

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Database Tables (Access)

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Database Tables (Oracle)

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DBMS Query ProcessorAll Data

Database EngineData Dictionary

Query Processor

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DBMS Report WriterAll Data

Database EngineData Dictionary

Query Processor

Report Writer

ReportFormat

and Query

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Report Writer (Oracle)

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DBMS Input FormsAll Data

Database EngineData Dictionary

Query Processor

Form Builder

InputForm

Design

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DBMS Components

All Data

Database EngineData Dictionary

Security

Query Processor

FormBuilder

ReportWriter

CommunicationNetwork

3GLConnector

Program

ApplicationGenerator

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Examples of Commercial Systems

Oracle Ingres Informix (Unix) DB2, SQL/DS (IBM) Access (Microsoft) SQL Server (Microsoft +) Many older (Focus, IMS, ...) Many limited PC (dBASE, Paradox, …)

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Hierarchical DatabaseCustomers

Orders

Item Description Quantity998 Dog Food 12764 Cat Food 11

Items

Customer

Order

Items Ordered

To retrieve data, you must start at the top (customer). When you retrieve a customer, you retrieve all nested data.

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Network Database

Customer

OrderItems

Ordered

Items

Entry point

Entry point

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Relational Database

Customer(CustomerID, Name, …

Order(OrderID, CustomerID, OrderDate, …

ItemsOrdered(OrderID, ItemID, Quantity, …

Items(ItemID, Description, Price, …

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Why don’t all developers use a DBMS?

Most new projects (in last 5 years) do use a DBMS Need specialized personnel

ProgrammersDesigners/AnalystsDatabase administrators

Need to define data for organization Cost

PC: $400 - $2000Large: $100,000 +

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DBMS approach

Applications change a lot, but same data. Need for ad hoc questions and queries. Need to reduce development times. Need shared data. Improve quality of data. Enable users to do more development.

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Database System Design

User viewsof data.

Conceptualdata model.

Customer(CustomerID, Name, Address, …)

SalesPerson(EmployeeID, Name, Commission, … )

Order(OrderID, OrderDate, CustomerID, EmployeeID, … )

OrderItem(OrderID, ItemID, Quantity, Price, … )

Item(ItemID, Description, ListPrice, …)

Implementation(relational)data model.

Physicaldatastorage.

Class diagram that shows business entities, relationships, and rules.

List of nicely-behaved tables. Use data normalization to derive the list.

Indexes and storage methods to improve performance.

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The Need for Design

Goal: To produce an information system that adds value for the userReduce costs Increase sales/revenueProvide competitive advantage

Objective: To understand the systemTo improve itTo communicate with users and IT staff

Methodology: Build models of the system

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Initial Steps of Design

1. Identify the exact goals of the system.

2. Talk with the users to identify the basic forms and reports.

3. Identify the data items to be stored.

4. Design the classes (tables) and relationships.

5. Identify any business constraints.

6. Verify the design matches the business rules.

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DefinitionsEntity: Something in the real world that we wish to describe

or track.Class: Description of an entity, that includes its attributes

(properties) and behavior (methods).Object: One instance of a class with specific data.Property: A characteristic or descriptor of a class or entity.Method: A function that is performed by the class.Association: A relationship between two or more classes.

Entity: Customer, Merchandise, SalesClass: Customer, Merchandise, SaleObject: Joe Jones, Premium Cat Food, Sale #32Property: LastName, Description, SaleDateMethod: AddCustomer, UpdateInventory, ComputeTotalAssociation: Each Sale can have only one Customer.

Pet Store Examples

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Associations General

One-to-one (1:1) One-to-many (1:M) Many-to-many (M:N)

Relationships represent business rules Sometimes common-sense Sometimes unique to an

organization

Users often know current relationships, rarely future

Objects related to objects An employee can work in

only one department Many departments can work

on many different products

Objects related to properties An employee can have only

one name Many employees can have

the same last name

1 * AnimalBreed

* *performs

TasksEmp1 *places

SaleCust.

places

1 * Purch.Order

Supplier

sent to

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Why Normalization?

Need standardized data definitionAdvantages of DBMS require careful designDefine data correctly It especially makes it easier to expand database laterMethod applies to most models and most DBMS

Similar to Entity-Relationship Goal: Define tables carefully

Save spaceMinimize redundancyProtect data

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Definitions Relational database: A collection of tables. Table: A collection of columns (attributes) describing an entity.

Individual objects are stored as rows of data in the table. Property (attribute): a characteristic or descriptor of a class or entity. Every table has a primary key.

The smallest set of columns that uniquely identifies any row Primary keys can span more than one column (concatenated keys) We often create a primary key to insure uniqueness (e.g., CustomerID,

Product#, . . .) called a surrogate key.

EmployeeID TaxpayerID LastName FirstName HomePhone Address12512 888-22-5552 Cartom Abdul (603) 323-9893 252 South Street15293 222-55-3737 Venetiaan Roland (804) 888-6667 937 Paramaribo Lane22343 293-87-4343 Johnson John (703) 222-9384 234 Main Street29387 837-36-2933 Stenheim Susan (410) 330-9837 8934 W. Maple

Employee

Properties

Rows/ObjectsClass: Employee

Primary key

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First Normal Form Problems (Data)TransID RentDate CustID Phone LastName FirstName Address City State ZipCode1 4/18/02 3 502-777-7575 Washington Elroy 95 Easy Street Smith's Grove KY 421712 4/30/02 7 615-888-4474 Lasater Les 67 S. Ray Drive Portland TN 371483 4/18/02 8 615-452-1162 Jones Charlie 867 Lakeside Drive Castalian Springs TN 370314 4/18/02 3 502-777-7575 Washington Elroy 95 Easy Street Smith's Grove KY 42171

TransID VideoID Copy# Title Rent1 1 2 2001: A Space Odyssey $1.501 6 3 Clockwork Orange $1.502 8 1 Hopscotch $1.502 2 1 Apocalypse Now $2.002 6 1 Clockwork Orange $1.503 9 1 Luggage Of The Gods $2.503 15 1 Fabulous Baker Boys $2.003 4 1 Boy And His Dog $2.504 3 1 Blues Brothers $2.004 8 1 Hopscotch $1.504 13 1 Surf Nazis Must Die $2.504 17 1 Witches of Eastwick $2.00

1NF splits repeating groups

Still have problems Replication Hidden dependency: If a video has not been

rented yet, then what is its title?

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Second Normal Form Definition

Each non-key column must depend on the entire key. Only applies to

concatenated keys Some columns only depend

on part of the key Split those into a new table.

Dependence (definition) If given a value for the key

you always know the value of the property in question, then that property is said to depend on the key.

If you change part of a key and the questionable property does not change, then the table is not in 2NF.

RentalLine(TransID, VideoID, Copy#, Title, Rent)

Depend only on VideoID

Depends on both TransID and VideoID

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Second Normal Form Example

Title depends only on VideoID Each VideoID can have only one title

Rent depends on VideoID This statement is actually a business rule. It might be different at different stores. Some stores might charge a different rent for each

video depending on the day (or time).

Each non-key column depends on the whole key.

RentalLine(TransID, VideoID, Copy#, Title, Rent)

VideosRented(TransID, VideoID, Copy#)

Videos(VideoID, Title, Rent)

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Second Normal Form Example (Data)

TransID VideoID Copy#1 1 21 6 32 2 12 6 12 8 13 4 13 9 13 15 14 3 14 8 14 13 14 17 1

VideoID Title Rent1 2001: A Space Odyssey $1.502 Apocalypse Now $2.003 Blues Brothers $2.004 Boy And His Dog $2.505 Brother From Another Planet $2.006 Clockwork Orange $1.507 Gods Must Be Crazy $2.008 Hopscotch $1.50

VideosRented(TransID, VideoID, Copy#)

Videos(VideoID, Title, Rent)

RentalForm2(TransID, RentDate, CustomerID, Phone,Name, Address, City, State, ZipCode)

(Unchanged)

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Third Normal Form Definition

RentalForm2(TransID, RentDate, CustomerID, Phone, Name, Address, City, State, ZipCode)

Each non-key column must depend on nothing but the key. Some columns depend on

columns that are not part of the key.

Split those into a new table. Example: Customers name

does not change for every transaction.

Dependence (definition) If given a value for the key

you always know the value of the property in question, then that property is said to depend on the key.

If you change the key and the questionable property does not change, then the table is not in 3NF.

Depend only on CustomerID

Depend on TransID

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