This document discusses key concepts about database management systems including: 1. It defines what data and databases are and how data is represented in computer systems using bits, bytes, words, and other units of storage. 2. It describes the components of databases including fields, records, tables, forms, reports and pages. 3. It explains the differences between flat file databases and relational databases and how relational databases better organize large amounts of data. 4. It provides an overview of how database management systems are used to enter, query, and manage database data.

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