Chapter11 Databases1 A file is a set of related records –A file is named by its owner –It is a user’s minimal accessible unit on secondary storage What

Chapter11 Databases 1

• A file is a set of related records – A file is named by its owner– It is a user’s minimal accessible unit on secondary

storage

• What if multiple people want to share information (perhaps about employees)– Do multiple files have the same information?

• Then how do we guarantee consistency when an update is made?

– Can we maintain a single file?• Then how do we guarantee proper access?

Databases

Database• A database is a collection of organized

information – In computer terms, information is contained in files

• Databases organize multiple files– Provide answers to complex queries

• Databases control access– Restrict rights to information

• Databases support data consistency– Every user’s view has the most current values


Database Management

• Database Management tasks include:– Collecting data– Updating data (adding and deleting)

• Working with static data is called data mining

– Storing data for efficient retrieval– Organization of data

• Sorting; securing access, etc.

– Outputting data – concurrency handled


Database Management

• Data input– The most problematic part of database

management– Humans may enter incorrect or partial values

• Handwriting may be illegible

• Keys or buttons may be punched incorrectly

– Sensors may enter incorrect data values– It is difficult to correct false information


Data Organization

• If you have a telephone directory, how do you insert a name in the middle?

• If you have a database, data can be inserted at the end (or wherever there is room) and the system will order it logically

• Do you have several lists of people that you have invited to different parties. Do they overlap? What if an address gets changed?


Databases in Use

• Banks, Credit Card Companies, Search engines, Super Markets with customer cards, charities all maintain databases– Mailing lists are generated by selecting:

• Name and Addresses from perhaps multiple files– Select name, address from *

– Selected names can be targeted based on attributes

– Select from * where last-payment-year < 2011


Data mining

• Data extracted from multiple databases and stored in data warehouse

• Data from operational (active) databases may also be extracted and copied to data warehouse

• Analysis can result in, for example,– Lower insurance rates based on expectations– Smaller reorders of inventory items


Predictive analytics• Statistical algorithms, neural networks, and

optimization research applied to data mining to find patterns in data– Predict the amount of money a state must set

aside for employee pensions– Predict the lottery numbers to be chosen this

May– Predict how much a house will appreciate in

value from 2007 to 2011


How to store data• Simplest way to store data is in a flat file

– For example, an Excel spreadsheet– Rows and columns in an Excel flat file

• Field- smallest building block

– Has a unique identifier

– Variable or fixed length

• Record: collection of related fields

– Medical records


Record type • Student record

– Name– ID– Starting Date– Courses enrolled in

• Note: typically an ID is the unique key for a specific student record

• Name, Id, date, courses are fields (attributes)


Record occurrence (instance)

• Name : John Doe

• ID : 0003456

• Starting Date : 1/12/09

• Courses : CSCI 1105; ENG 2001

Data fields are variable in length; data values are typically assigned and changed dynamically.

Course attributes doesn’t fit with the other static data.


Relationships• “A relationship is an association between

data that is stored in different record types”

• Given: a file of student records

• Given: a file of courses (with attributes of course #, room #)

• Relationship– For each student in the student record file, find

the classroom that they are in on Monday April 7th (if any)


Relational Database Mgmt Systems

• Collections of related tables– Think of an Excel spreadsheet– Each table is a sequence of records

• Each row is a record instance• Each column defines attributes (field)


Vintage Music Shop (from text)

• Table 1

• AlbumsCat# Title ArtistName ReleaseDate InStock SellingPrice

1011 AA Ella 2/10/59 no 45.95

1010 BB George 2/15/64 yes 22.05

1101 CC William 4/1/00 yes 5.85

Each record must have a unique key (possibly combined fields)


Vintage Music Shop

• Table 2

• OrdersOrderNumber CustomerNumber Total OrderDate


Vintage Music Shop

• Table 3

• OrderDetailsOrderNumber CatNumber Quantity DiscountPrice


Vintage Music Shop

• Table 4

• Customers

Cust ID FirstName LastName Street City Tel#


Vintage Music Shop

• Table 5

• AlbumDetails

Cat# TrackTitle TrackLength TrackSample


How to partition data into tables?

• You don’t want customers and orders in one table.– A customer might have many orders

• You don’t want orders and order details in one table– Order details lets you access the specific item

and quantity for inventory purposes– Orders are for billing customer


Database design is not obvious

• Just like PowerPoint, it takes some practice to separate information

• Placing information in different “modules” makes it easier to handle


Dimensional Database Systems

• Your multi-worksheets for drugstore inventory were 3-dimensional– Rows – different items handled– Columns – sales each month– Years 2009/2010 were a 3rd dimension

• Relational database systems can be 3-dimensional


Object oriented databases• Data are stored as objects

• Objects are grouped into classes– Each object is an instance of a class

• Attributes for the class are the same as fields

– Valid methods are also defined for the class• For Vintage Record Company, method for the class

Orders might include checkInventory, checkCustomerCredit


Inheritance in Object-oriented databases

• If different records have some different attributes, the database might have to contain different record types– Customer form for phone or web customers

• In object-oriented databases, methods are defined on the class type and differentiated for different types of orders


Relational and OO databases

• Some relational databases have been modified to include object-oriented features– SQL, besides being used for queries, can also

be used to define functions, such as for playing a song


Data management with spreadsheets

• Columns// fields or attributes

• Rows// records or instances

• Methods// sort, search, some mathematical functions, graphs

• Visual Basic code, macros can be inserted into Excel for other functions


Types of DBMS• Entry level

– Microsoft Access• Cannot scale up to large amounts of traffic

• Public domain SQLite

• Database server software– Oracle Database– IBM DB2– Microsoft SQL Server– Sun’s open source MySQL


Database access through the Web

• Static Web publishing– Convert database report into HTML document

• Displayed by browser

– Data is read only; it’s not changed dynamically– Secure (read access-- to web page , not to

database)– Simple (access allows you to “export” the data

as an HTML or XML file)


“view” in databases

• It is possible to allow different users to see only part of the data– This is called a view

• Providing views on the web requires server-side programming– Cookie on customer (client) site provides client

identification– Client id is used to generate a query to the DB


Updating a database• Clients can be provided rights to make

changes in the data values– Not changes in attributes – that is DBMS function

• On the web, a form is provided to customers– HTML forms, for example, with JavaScript

• Server-side programs such as ASP, CGI, PHP, ColdFusion process client input


XML

• XML as a standard for client output and input

• alpha.fdu.edu/~levine/xml/albums.xml

• alpha.fdu.edu/~levine/xml/album1.xml


Documents

Chapter11 Databases1 A file is a set of related records –A file is named by its owner –It is a user’s minimal accessible unit on secondary storage What