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1. Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.McGraw-Hill Technology Education
Chapter 11A
Database Management
Systems

2. Data
• Information in raw or unorganized form
(such as alphabets, numbers, or
symbols) that represent, conditions,
ideas, or objects.
• In computing, data is information that
has been translated into a form that is
more convenient to process.
11A-2

3. Data Representation
1. Bits
– A bit is the fundamental unit of computer
storage
– A bit can be 0 (off) or 1 (on)
– Related bits are grouped to represent
different types of information such as
numbers, characters, pictures, sound,
instructions
11A-3

4. 4
Nibbles
• Nibbles
– A nibble is a group of
4 bits
– A nibble is used to
represent a digit in
Hex (from 0-15) and
BCD (from 0-9)
numbers
BCD Hex
0000 0 0
0001 1 1
0010 2 2
0011 3 3
0100 4 4
0101 5 5
0110 6 6
0111 7 7
1000 8 8
1001 9 9
1010 A
1011 B
1100 C
1101 D
1110 E
1111 F

5. Data Representation inData Representation in
Computer SystemsComputer Systems
5
Bytes
Bytes
– A byte is a group of 8 bits that is used to
represent numbers and characters
– A standard code for representing numbers
and characters is ASCII (American
Standard Code for Information
Interchange )

6. Data Representation inData Representation in
Computer SystemsComputer Systems
6
Byte Size
Bytes
– How many different combinations of 0’s and
1’s with 8 bits can be formed?
– In general, how many different
combinations of 0’s and 1’s with N bits can
be formed?
– How many different characters can be
represented with a byte (8 bits)?

7. Data Representation inData Representation in
Computer SystemsComputer Systems
7
Words
Words
– A word is a group of 16 bits or 2 bytes
– UNICODE is an international standard code
for representing characters including non-
Latin characters like Asian, Greek, etc.

8. Data Representation inData Representation in
Computer SystemsComputer Systems
8
Double Words
Double Words
– A double word is a group of 32 bits or 4
bytes or 2 words

9. Related Bytes
– A nibble is a half-byte (4-bit) - hex representation
– A word is a 2-byte (16-bit) data item
– A doubleword is a 4-byte (32-bit) data item
– A quadword is an 8-byte (64-bit) data item
– A paragraph is a 16-byte (128-bit) area
– A kilobyte (KB) is 210
= 1,024 bytes ≈ 1,000 bytes)
– A megabyte (MB) is 220
= 1,048,576 ≈1 Million Bytes
– A Gigabyte (GB) is 230
= 1,073,741,824 ≈ 1 Billion

10. Database approach
• The database approach is a way in
which data is stored within a
computer.
• It is organized into various charts that
are accessed by a variety of computer
applications from different locations.
• Databases are composed of a variety of
information that is relevant to the
organization that is using the database.
11A-10

11. 11A-11
Database Management Systems
• Database management system (DBMS)
• Store large collections of data
• Organize the data
• Becomes a data storage system

12. 11A-12
The Database
• A database is a collection of information
that is organized so that it can easily be
accessed, managed, and updated.
• Stores a collection of related items
• Collection is arranged in a structure
– Organizes and describes the data
• Examples:
• Library database, Police database,
medical store database etc

13. 11A-13
Database Structure
Field NameField Name
RecordRecord
FieldField

14. 11A-14
Components of Database
• 1. Fields
– Hold an individual piece of data
– Are named descriptively
– Often called a column
– Phone book examples
• Name, address, e-mail, phone number
– Fields may contain no data

15. 11A-15
Components of Database
• 2. Records
– One full set of fields
– Often called a row
– Phone book example
• Smith, Joe, 123 Some Street, 412-555-7777
– Databases may have unlimited rows

16. 11A-16
Database Helper Documents
• 4. Forms
– forms are designed to ease the data entry process.
For example, you can create a data entry form that
looks exactly like a paper form . People generally
prefer to enter data into a well-designed form,
rather than a table.

17. 11A-17
Components of Database
• 5. Tables
Tables are where the actual data is defined
and entered. Tables consist of records
(rows) and fields (columns).
• 6. Reports
– Produce printed results from the database
– Includes tools to summarize data

18. 11A-18
Database Helper Documents
• 7. Pages: a data access page is a
special type of Web page designed for
viewing and working with data from the
Internet or an intranet. This data is
stored in a Microsoft Access database
or a Microsoft SQL Server database.

19. Database types
1. Flat file database
2. Relational database
11A-19

20. 11A-20
Flat-file Databases
• Typically has only one table
– If multiple, each has a separate file
• Useful for simple data storage needs
• Hard to manage large data needs
• Can waste disk space

21. 11A-21
Relational Databases
• Made of two or more tables
• Tables are related by a common field
– Called a relationship or join
– Can help organize data
• Most common form of database
• Maintaining data is easier than flat-file
• No wasted disk space

22. 11A-22
Database Management System
• Programs that control the database
• Allows
– Entering data
– Querying data
– Printing reports
• Supports thousands of users
• Includes tools to protect the data

23. 11A-23
Working with a Database
• Querying a database
– Statement that describes desired data
– List of fields can be modified
– Uses of querying
• Find data
• Calculate values per record
• Delete records
– Most important DBMS skill

24. 11A-24
Working with a Database
• Query languages
– All DBMS use a query language
• Most DBMS modify the language
– Structured Query Language (SQL)
• Most common query language
– xBase
• Query language for dBase systems
– Query by example (QBE)
• Interface to SQL or xBase
• Interactive query design

25. Data Dictionary
• A data dictionary is a file or a set of files
that contains a database's metadata.
The data dictionary contains records
about other objects in the database,
such as data ownership, data
relationships to other objects, and other
data.
11A-25