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Chapter 22
Organizing Data and Information
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What is a database
A database is any organized collection ofdata. Some examples of databases youmay encounter in your daily life are:
a telephone book
T.V. Guide
airline reservation system
motor vehicle registration records papers in your filing cabinet
files on your computer hard drive.
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Why do we need a database?
Keep records of our:
Clients
Staff
Volunteers
To keep a record of activities and
interventions;
Keep sales records;
Develop reports;
Perform research
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What is the ultimate purpose of a
database management system?
Data Information Knowledge Action
Is to transformIs to transform
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DATAData
A necessity for almost any enterprise tocarry out its business. Consists of raw facts,and when organized may be transformed
into informationDatabase
A collection of data organized to meet usersneeds
Database management system (DBMS) A group of programs that manipulate the
database and provide an interface betweenthe database and the user of the database orother application programs
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Data vs. information:
What is the difference? What is data?
Data can be defined in many
ways. Information science
defines data as unprocessedinformation.
What is information? Information is data that have
been organized and
communicated in a coherent
and meaningful manner.
Data is converted into
information, and information
is converted into knowledge.
Knowledge; information
evaluated and organized sothat it can be used
purposefully.
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DBMSA collection of programs that enables you to store,
modify, extract information from a database. There aremany different type of DBMSs, ranging from small
systems that run on personal computers to huge systems
that run on mainframes. The following are examples ofdatabase applications:
computerized library systems
automated teller machines
flight reservation systems
computerized parts inventory systems
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TerminologyDatabase
A collection of integrated and related files
File A collection of related records
Record A collection of related fields
Field A group of characters
Character Basic building block of information, represented
by a byte
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Data Entities, Attributes, andKeysEntity
A generalized class of people, places, or things(objects) for which data are collected, stored, andmaintained E.g., Customer, Employee
Attribute A characteristic of an entity; something the entity
is identified by E.g., Customer name, Employeename
Keys A field or set of fields in a record that is used to
identify the record E.g, A field or set of fieldsthat uniquely identifies the record
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The Traditional Approach
The traditional approach
Separate files are created and stored for each
application program
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Drawbacks
Data redundancy
Duplication of data in separate files
Lack of data integrity The degree to which the data in any one file is
accurate
Program-data dependence
A situation in which program and data organized forone application are incompatible with programs and
data organized differently for another application
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Database Approach
The database approach
A pool of related data is shared by multiple
application programs Rather than having separate data files, each
application uses a collection of data that is
either joined or related in the database
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Advantages
Improved strategic use of corporate data
Reduced data redundancy
Improved data integrity
Easier modification and updating Data and program independence
Better access to data and information
Standardization of data access
A framework for program development Better overall protection of the data
Shared data and information resources
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Disadvantages
Relatively high cost of purchasing and
operating a DBMS in a mainframe operating
environment
Increased cost of specialized staff
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Data Modeling and
Database Models (2) Data model
A map or diagram of entities and their relationships
Enterprise data modeling Data modeling done at the level of the entire
organization
Entity-relationship (ER) diagrams
A data model that uses basic graphical symbols toshow the organization of and relationships between
data
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Hierarchical Database Model
Hierarchical database model
A data model in which data are organized in a
top-down, or inverted tree structure
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Department C
Employee
1
Employee
2
Employee
3
Employee
4
Employee
5
Employee
6
Department B
Project 1
Department A
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Network Data Model
Network data model
An expansion of the hierarchical database model
with an owner-member relationship in which a
member may have many owners
Project 1 Project 2
Department A Department B Department C
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Relational Data Model
Relational data model
All data elements are placed in two-
dimensional tables, called relations, that arethe logical equivalent of files
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The Relational Model
Views entities as two-dimensional tables
Records are rows
Attributes (fields) are columns Tables can be linked
Supports one-to-many, many-to-many, and
one-to-one relationships
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Project
NumberDescription
Dept.
Number
155 Payroll 257
498 Widgets 632
226Sales
manager
598
Dept. Number Dept. Name Manager SSN
257 Accounting 421-55-99993
632 Manufacturing 765-00-3192
598 Marketing 098-40-1370
SSN Last Name First Name Hire Date Dept. Number
005-10-6321 Johns Francine 10-7-65 257
549-77-1001 Buckley Bill 2-17-79 650
098-40-1370 Fiske Steven 1-5-85 598
Data Table 1: Project Table Data Table 2: Department Table
Data Table 3: Manager Table
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Schemas and Subschemas
Schema
A description of the entire database
Subschema A file that contains a description of a subset of
the database and identifies which users can
perform modifications on the data items in
that subset
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DBMS
Schema
Subschema
B
Subschema
A
Subschema
C
User
1
User
2
User
3
User
4
User
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Emp_Id First_Name Last_Name Department
001234 Ignacio Fleta Accounting
002000 Christian Martin Computer Support002122 Orville Gibson Human Resources
003400 Ben Smith Accounting
003780 Allison Chong Computer Support
Database Table
Row
(Record)
Column Field
Each table has a primary key Uniquely identifies that row of the table Emp_Id is the primary key in this example Serves as an index to quickly retrieve the record
Columns are also calledfields orattributes Each column has a particular data type
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SQL
Structured Query Language, abbreviated
SQL
Usually pronounced sequel but also ess-cue-ell) The common language of client/server database
management systems.
Standardized you can use a common set of SQL
statements with all SQL-compliant systems.
Defined by E.F. Codd at IBM research in 1970.
Based on relational algebra and predicate logic
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Queries
Queries are the information retrieval
requests you make to the database
Your queries are all about the informationyou are trying to gather
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Reports
If the query is a question...
...then the report is its answer
Reports can be tailored to the needs of thedata-user, making the information they
extract much more useful
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Data Dictionary
Data Dictionary
A detailed description of all data used in the
database
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Data Dictionary Features
Provide a standard definition of terms anddata elements
Assist programmers in designing and writing
programs Simplify database modification
Reduce data redundancy
Increase data reliability
Faster program development
Easier modification of data and information
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Data Definition Language
Data Definition Language (DDL)
A collection of instructions and commands
used to define and describe data and datarelationships in a specific database
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Database Transactions
1. DML
2. DDL
3. DCL
Transaction starts with an execution of SQLstatements and ends with one of the following:
COMMIT or ROLLBACK
DDL or DCL (automatic commit)
user exits or quits
system crashes
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A cell is also called a FIELD.
A number of such field placed in
horizontal plane is called a RECORD or arow.
To create a cell in which a user can store
and maintain data,the DBA requires aminimum of three parameters by user.
Cell name, Cell length, Cell data type.
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These parameters are passed to the DBAvia its natural language,SQL.
Various Datatypes: Char(max len 255)
Varchar(max len 2000)
Number
Date(dd/mm/yy)
Long(len upto 65,535)
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Choosing Column Names
Define a column for each piece of data Allow plenty of space for text fields
Avoid using spaces in column names
For the members of an organization:Column Name Type Remarks
Member_ID int Primary key
First_Name varchar(40)
Last_Name varchar(40)
Phone varchar(30)Email varchar(50)
Date_Joined smalldatetime Date only, no time values
Meetings_Attended smallint
Officer Yes/No True/False values
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22.4 SQL (Structured Query
Language)SQL keyword DescriptionSELECT Selects (retrieves) columns from one or more tables.FROM Specifies tables from which to get columns or delete
rows. Required in every SELECT and DELETE
statement.WHERE
Specifies criteria that determine the rows to beretrieved.INNERJOIN Joins rows from multiple tables to produce a single
set of rows.GROUPBY Specifies criteria for grouping rows.ORDERBY Specifies criteria for ordering rows.INSERT Inserts data into a specified table.UPDATE
Updates data in a specified table.DELETE Deletes data from a specified table.CREATE Creates a new table.DROP Deletes an existing table.COUNT Returns the number of records that satisfy given
search criteria.
Fig. 22.12 SQL keywords.
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22.4.1 Basic SELECT Query
SELECT * FROM tableName
SELECT * FROM Authors
SELECT authorID, lastName FROMAuthors
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22.4.1 Basic SELECT Query
author
last ame author
last ame
1 eitel 7 adhu
2 eitel 8 c hie
3 Nieto 9 aeger
4 teinbuhler 10 Zlatkina
5 antry 11 Wiedermann
6 in 12 iperiFi . . 3 author
last ame fr t
uthors t bl .
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The create table command:
CREATE TABLE tablename(columnname datatype(size),
columnname datatype(size));
Eg:CREATE TABLE client(client_no
varchar2(6),name varchar2(20),add
varchar2(30),pincode number(6),bal_due
number(10,2));
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insertion
INSERT INTO tablename
[(columnname,columnname)]
Values(expression,expression); INSERT INTO client
(client_no,name,add,Pincode)
VALUES(c123,lovely,phagwara,144444);
NOTE:character expression in single quotes
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Updation
UPDATE tablename SET
columnname=expression,
columnname=expression WHEREcolumnname=expression;
UPDATE client SET
name=university,add=jalandharWhere client_no=c123;
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Deletion
DELETE FROM tablename; DELETE FROM client;
DELETE FROM client WHERE
client_no=c123;
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Controlling Transactions
An automatic commit occurs under the
following circumstances:
DDL statement is issued DCL statement is issued
normal exit from SQL, without explicitly
issuing COMMIT or ROLLBACK
Abnormal Termination
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COMMIT & ROLLBACK
INSERT, DELETE, & UPDATE data
from a database can be reversed
(ROLLBACK) or committed (COMMIT) Show AUTOCOMMIT
ROLLBACK
COMMIT SET AUTOCOMMIT ON
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State of Data Before COMMIT
or ROLLBACK The previous state of the data can be recovered
The current user can review the result of the
DML operation by using SELECT Other user cannot view the result of the DML
statements by the current user
The affected rows are locked (other users can not
change the data within the affected rows)
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State of the Data after COMMIT
Data changes are made permanent in DB
The previous state of the data is
permanently lost All users can view the results
Locks are released
All saved points are erased
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Committing Data
UPDATE student
SET major = COSC
WHERE id = 111;
COMMIT;
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State of the Data after ROLLBACK
Data changes are undone
Previous state of the data is restored
Locks on the rows are released
DELETE FROM student;
10,000 records are deleted
ROLLBACK;
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Controlling Transactions
INSERT UPDATE INSERT DELETE
Rollback
Rollback
Rollback
Rollback
Point BPoint ACOMMIT
Transaction
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Roll Back Changes to a Marker
SAVEPOINT PointA;
..
SAVEPOINT PointB;..
ROLLBACKTO PointB;
ROLLBACK;
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Distributed Databases
Distributed database
A database in which the actual data may be
spread across several smaller databases
connected via telecommunications devices
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Data Warehouse
Data warehouse
A relational database management system designed
specifically to support management decision making
Current evolution of Decision Support Systems(DSSs)
Data mart
A subset of a data warehouse for small and medium-
size businesses or departments within largercompanies
Schematic
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Relational
databases
Hierarchicaldatabases
Network
databases
Flat files
Spreadsheets
Data
extractionprocess
Query and
analysis
tools
Data
wharehouse
Data
cleanup
process
End user access
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Data Mining Applications
Data mining
The automated discovery of patterns and relationships
in a data warehouse
Data mining applications Market segmentation
Customer queries
Fraud detection
Direct marketing Market basket analysis
Trend analysis
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Object-Relational Database
Management Systems (ORDBMS)
Object-relational database management system (ORDBMS) A DBMS capable of manipulating audio, video, and graphical data.
Hypertext
Users can search and manipulate alphanumeric data in an unstructuredway
Hypermedia
Allows businesses to search and manipulate multimedia forms of data
Spatial data technology
Use of an object-relational database to store and access data accordingto the location it describes and to permit spatial queries and analysis
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THATS ALL