Introduction to Database Systems

1. Introduction to Database
Systems

2. Course Details
 Textbook
◦ Database Systems Concepts Design Applications by S K
Singh, latest edition 2011
 Reference
◦ Database System by Catherine Ricardo
◦ Data Management Systems by Raghu Ramakrishnan and
Johannes Gehrke
◦ Database Systems: Design, Implementation, and
Management By Carlos Coronel, Steven Morris, Peter
Rob, 10th edition 2012
◦ An Introduction to Database Systems By Date, 2006
◦ Introduction To ORACLE: SQL and PL/SQL, Student
Guide, Production 1.1, Volume 1.2.
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3. Course Outline
(subject to minor changes)
 Basics: Introduction to Database Systems, The Entity Relationship
Model, The Relational Model, Relational Algebra and Calculus
 SQL: Queries, Programming, Triggers, Query By Example (QBE)
 Data Storage and Indexing: File Organization and Indexes, Tree
Structured Indexing, Hash Based Indexing
 Query Evaluation: External Sorting, Evaluation Of Relational
Operators, Introduction to Query Optimization, A Typical Relational
Query Optimizer
 Database Design: Schema Refinement and Normal Forms, Physical
Database Design and Tuning, Security
 Transaction Management: Transaction Management Overview,
Concurrency Control, Crash Recovery
 Advanced topics: Parallel and Distributed Databases, Internet
Databases, Decision Support, Data Mining, Object Database Systems,
Spatial Data management, Deductive Databases 3

4. Introduction
 In today’s competitive environment, data and its
effective management is the most critical business
objective of an organization
 The success of an organization is now dependent on its
ability to acquire accurate, reliable and timely data
about its business or operation for effective decision
making process
 Database system is a tool that simplifies the above
tasks of managing and extracting useful information,
analyses and guided the activities of an organization
 It is the central repository of the data in organization
information system: maintain the data, support
organization function and help in decision making
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5. What are Data?
 Data may be defined as a fact that can be recorded and
have implicit meaning
 Data are often viewed as the lowest level of abstraction
from which information and knowledge are derived.
 Data can exist in a variety of forms -- as numbers or
text on pieces of paper, as bits and bytes stored in
electronic memory, or as facts stored in a person's mind.
 Raw data refers to a collection of numbers, characters,
images or other outputs from devices that collect
information to convert physical quantities into symbols,
that are unprocessed.
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6. What are Data?
 Usually, there are many facts to describe something of
interest to us. (For example, employee data to calculate
payroll check, send company greetings, inform family
in case of emergency
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Data: Where can we find it?
Memories
Folders
Spreadsheets Paper piles
Lists
Filing Cabinets
And many more …

8. Information
 Information is processes, organized or summarized data
 It may be defined as a collection of related data that
when put together, communicate meaningful and useful
message to the recipient who use it to make decision
 Data are processed to create the information, which is
meaningful to the recipient
 It helps in giving warning signals before something
starts going wrong
 It predicts the future with reasonable level of accuracy
and helps the organization to make the best decisions.
 Database may contain either data or information or
both.
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9. Information
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10. Data Versus Information
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11. Data Versus Information
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12. Data Versus Information
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13. Data Item or Field
 A data item is the smallest part of data that has meaning to
its user called field or data element
 It is the occurrence of smallest unit of named data
 It is represented in the database by a value
 Example: Name, telephone number, bill amount, address
and so on.
 Data items are the modules of the database
 A data item may be used to construct other, more complex
structures
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14. Records
 A record is a collection of logically related fields or
data items, with each field having a fixed data type
 A record consists of values for each field
 Data items are grouped together to form a record.
 recover or updated using programs.
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15. Files
 A file is a collection of related sequence of records
 Fixed-length records: Every record in the file has exactly
the same size
 Variable-length records: different records in the file has
different sizes.
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16. Example
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17. File Oriented Systems
 Computer based filing system were initially used for
scientific and engineering calculations
 Manual Method of filing of an organization
◦ Hold internal and external correspondence relating to project
◦ File and folders were labeled and stored in cabinets under
lock for safety and security reasons
◦ Difficult to search specific entry in specific file and folder
◦ Work well for small data
◦ Report generation from manual file system could be slow
and cumbersome
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18. File Oriented System
 A file system is a method of storing and organizing
computer files and their data.
 basically, it organizes these files into a database for
the storage, organization, manipulation, and recovery
by the computer's operating system.
 Since it perform normal record keeping functions,
called data processing systems
 File systems are used on data storage devices such as
a hard disks or CD-ROMs to maintain the physical
location of the files.
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19. File Oriented System
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20. File Oriented System
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21. File Oriented System
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File Systems
 ASCII file
 Accounts separated by new lines
 Fields separated by #’s
 Different files: account types, branches etc.

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File Systems
 What’s the balance in Homer Simpson’s account?
 A simple script
 Scan through the accounts file
 Look for the line containing “Homer Simpson”
 Print out the balance

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File Systems

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Advantages of File System
 Provides a useful historical perspective that how we
handle the data
 Helps in overall understanding of design complexity
of the overall system
 Understanding the problems and knowledge of
limitation in file based system helps in avoiding the
same problem when designing database system.

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Drawbacks of File System
 Data Redundancy (or duplication)
◦ Decentralized approach adopted
◦ Duplication of information in different files (For example,
cust_id data in CUSTOMER and SALES file)
◦ Wasteful (more storage space, extra time and money, more
effort to keep data up to date)

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Drawbacks of File System
 Data Inconsistency (or loss of data integrity)
◦ Multiple file formats, duplication of information in different
files (e.g name in one file is 15 characters, while in other
file is 10 characters)
◦ Various copies of the same data may be different
◦ Results in maintenance overhead and storage costs
◦ Serious degradation in the quality of information and also
the accuracy

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Drawbacks of File System
 Difficulty in Accessing Data
◦ Need to write a new program to carry out each new task
 Data Isolation
◦ Data scattered in various files - Difficult
 Program Data Dependence
◦ A change in file structure requires change in the file
description (physical structure, storage of the data files and
record) in each program to confirm the new file structure
◦ Difficult to locate all files affected by it
◦ Time consuming and subject to error when making changes

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Drawbacks of File System
 Poor data control
◦ Multiple names used by various departments due to
decentralized nature
◦ Lead to different meanings of the data field in different
context, same meaning for different fields, leads to poor data
control, and also confusion
 Limited Data Sharing & Excessive Programming Effort
◦ Each application has its own private files
◦ Little opportunity to share data with other applications
◦ To obtain data from several incompatible files in separate
system will require a large programming effort
 Inadequate data manipulation capabilities
◦ No connection between data in different files, so data
manipulation capability is limited

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Drawbacks of File System
 Integrity Problems
◦ Integrity constraints (e.g. account balance > 0) become part
of program code
◦ Hard to add new constraints or change existing ones
 Atomicity Problems
◦ Failures may leave database in an inconsistent state with
partial updates carried out
◦ E.g. transfer of funds from one account to another should
either complete or not happen at all

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Drawbacks of File System
 Concurrent access by multiple users
◦ Concurrent accessed needed for performance
◦ Uncontrolled concurrent accesses can lead to
inconsistencies
 For example, two people reading a balance and updating
it at the same time
 Security Problems
◦ Access Control
Database systems offer solutions to all the above
problems

32. What is a Database?
 A database consists of an organized collection of data
for one or more multiple uses.
 An organized body of related information.
 A collection of logically related data stored together
that is designed to meet the information needs of the
organization
 A database is organized in such a way that a computer
program can quickly select desired pieces of data
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33. Database Applications
 Databases play a critical role in almost all areas
◦ Banking: all transactions
◦ Airline: reservation, schedules
◦ Universities: registration, grades
◦ Sales: customers, products, purchases
◦ Manufacturing: production, inventory, orders, supply
chain
◦ Human resources: employee records, salaries, tax
deductions
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34. What is a Database?
 A database can be of any size and of varying
complexity.
 A software system that facilitates the creation and
maintenance and use of an electronic database
◦ For example, the list of names and addresses of friends
◦ The book catalog of a large library may contain half a
million records
◦ A database of much greater size and complexity is
maintained to keep track of the tax information filed by
taxpayers.
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35. What is Database Management?
 Database management is an approach to provide
simplistic access to information stored in databases.
 Generalized software system for manipulating the
database
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36. What is a Database Management System?
 A DBMS is a collection of software programs to
enable users to create, maintain and utilize a database.
 DBMS is a generalized software system for
manipulating databases
◦ Process of Defining (specifying the data types, structure and
constraint)
◦ Constructing (process of storing data on storage media)
◦ Manipulating (querying to retrieve specific data, updating to
reflect changes and generating reports from the data)
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37. DBMS Components
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38. DBMS Components
 Data Definition Language
◦ Allows user to define database, constraints on the data to be
stored in the database
 Data Manipulation Language and query facility
◦ Allows user to insert, update delete and retrieve the data from
the database
◦ Provide general query facility through structured query
language (SQL)
 Software For controlled access of data
◦ Provides controlled access to the database
◦ For example, unauthorized user trying to access the database
◦ Providing concurrency control system to allow shared access
of the database
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39. 39
Database Management System

40. What is a DBMS?
 Functions of DBMS
◦ Insert records
◦ Delete records
◦ Update records
◦ Query records
◦ Add and Delete files from the database
 In short, DBMS comprises of two main parts
◦ Data Management in the database
◦ User Management associated with the database
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41. Database Approach
 Database system consists of logically related data
 Database approach represents the change in the way
end user data are stored, accessed and managed
 Emphasizes the integration and sharing of data through
the organization
 Eliminate problems related with data redundancy and
data control by supporting an integrated and centralized
data structure
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42. File Oriented versus Database Systems
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43. File Oriented versus Database Systems
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44. What is a DBMSs?
 Commercial DBMSs
Company Product
Oracle Oracle 8i, 9i, 10g,11i
IBM DB2, Universal Server (from System
R, System R*, Starburst) & Informix
Microsoft Access, SQL Server
Sybase Adaptive Server
Informix Dynamic Server
NCR Teradata
UC Brekeley’s INGRES,M PostgreSQL
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45. Advantages of DBMS
 Minimal Data Redundancy
◦ Centralized database and control of data
◦ Eliminates extra processing to trace the required data
◦ Storage requirement also reduced
◦ If duplicate data exists, DBMS is aware of it and ensure
multiple copies are consistent
 Program Data Independence
◦ Separation of data description from the application
programs
◦ Change in the data description does not affect the
application program that process the data
◦ Allow change at one level of the database without affecting
other levels
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46. Advantages of DBMS
 Efficient Data Access
◦ Utilize a sophisticated techniques to store and retrieve data
efficiently
 Improved Data Sharing
◦ Centralized repository of data belonging to entire
organization (For example, university data)
◦ Can be shared by all authorized users
◦ New application program can be developed on the existing
data in the database to share the same data and add only that
data that is not currently stored, rather having to define all
data requirements again
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47. Advantages of DBMS
 Improved Data Consistency
◦ Inconsistency is the corollary to redundancy
◦ DBMS ensures that any change made to either of the two
entries in the database is automatically applied to the other
one as well, known as propagating updates
 Improved Data Integrity
◦ Ensures that the data is accurate and consistent
◦ Rules that the database should not violate
◦ Centralized control of the data in the database system
ensures that adequate checks are incorporated in DBMS to
avoid data integrity problem
◦ For example, months between the range 01 and 12, not
allowed to transfer money less than specific amount
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48. Advantages of DBMS
 Improved Security
◦ Protection of database from unauthorized user
◦ Can define user name and passwords to authorize user, and
may be restricted for each type of access
◦ Different levels of security could be implemented for
various types of data and operations
 Increased Productivity of Application Development
◦ Provide many of the standard functions, such as forms and
report generators to automate some of the activities of the
database design
◦ Simplify the development of the database applications
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49. Advantages of DBMS
 Enforcement of Standards
 Economy of Scale
 Balance of Conflicting Requirements
 Improved Data Accessibility
 Improved Responsiveness
 Increased Concurrency
 Reduced Program Maintenance
 Improved Backup and Recovery Services
 Improved Data Quality
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50. Disadvantages of DBMS
 Increased Complexity
◦ Multi-user DBMS becomes an extremely complex piece of
software
◦ Necessary to understand the whole design to take advantage
of it
◦ Failure to understand, results in bad design decisions
 Requirement of New and Specialized Manpower
◦ Need to hire, train and retrain manpower on regular basis to
design and implement databases
◦ Need to maintain specialized skilled manpower
 Large Size of DBMS
◦ Requires large amount of memory to run efficiently due to
large complexity and wide functionality
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51. Disadvantages of DBMS
 Increased Installation & Management Cost
◦ Require trained manpower to install and operate DBMS,
also requires upgrade to the hardware, software and data
communication system
◦ Substantial training is required on ongoing basis to keep up
with new releases and upgrades
 Conversion Cost
◦ From legacy system to modern DBMS environment
◦ It includes cost of DBMS, hardware, cost of employing
specialists
 Need for Explicit Backup & Recovery
◦ Comprehensive procedure is required for the backup copies of
data and restoring a database when damage occurs
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52. Disadvantages of DBMS
 Additional hardware cost
 Organizational Conflict
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53. References
 Chapter 1, Database Systems, S K Singh
 Chapter 1, Database System Concepts, Silberschatz, Korth, Sudarshan
 Chapter 1, Database Management Systems, by Ramakrishnan and
Gehrke
 Course material from:
◦ Introduction to database systems – Duke University
◦ Database Systems – MCS Fall 2009
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