dbms lecture 01

8/13/2019 DBMS Lecture 01

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ELE320_ENGR. J. SADOL 1

ELE320 - Elective 1

Database Management Systems

Overview

Engr. Joy N. Sadol


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2

Data VS InformationData is a collection of raw facts

Examples:

customer name, graphics, images,address, sound, and video segments,telephone number

Data is not information

Data without context is useless


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Data VS Information The termsdata andinformation are

closely related, and in fact are often

used interchangeably.

Informationis data that has been

processed in such a way that it can

increase the knowledge of the personwho uses it.

Informationisdata that is organized

and meaningful.


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Data VS Information

Data + Interpretation -

>Information/KnowledgeExample:

Baker, Kenneth D. 2001-12345Doyle, Joan E. 1999-67890Finkle, Clive R. 2000-00001Lewis, Clark C. 1998-01023


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Data VS InformationConverting data to information (by

context)Class ListCourse: Filedat Trimester: 1st 01-02

Section: S33

Name Student Number Major GPA

Baker, Kenneth D. 2001-12345 SSE 3.5

Doyle, Joan E. 1999-67890 COE 3.0

Finkle, Clive R. 2000-00001 SSE 2.5Lewis, Clark C. 1998-01023 CNE 3.5


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Data VS InformationConverting data to information (summarized)Percent of Enrollment by Major (200X)

SSE 35%

COE 30%

CNE 35%

Data is a very powerful asset!

Steps in converting Data

to Information

Acquisition

Storage

Manipulation

Retrieval

Distribution


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Programs VS Systems Program - a set of step-by-step

instructions that directs a computer to

perform specific tasks and producecertain results.

Examples:

Sorting, adding numbers, computation oftaxes, computation of deductions, MS

Excel, MS Word, etc.


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Programs VS Systems System - an organized set of related

components established to perform a

certain task.

Examples:

Payroll System, MS Office System,

Inventory System, HRIS, DBMS etc.


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What is a Database?A collection of data, typically

describing the activities of one or more

related organizations It is a collection of data organized in a

way that allows

access retrieval use


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What is a Database? 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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What is a Database? A database can be of any sizeand of

varying complexity.

For example, the list of names and address offriends

The book catalog of a large library may containhalf a million records

A database of much greater size and complexity ismaintained by the government to keep track ofthe tax information filed by taxpayers.


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What is a Database?

A schemais the definition of a database. It definesthe meaning of data.

An instanceof a database is the collection of data inthe database at a particular point of time (snap-shot).

For example, in the above, the schema is StudentName, ID, Age, Gender, Entrance Year, Grade. Theremaining rows in the table make up an instance ofthe database.


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What is a DBMS? DBMS Database Management System

A DBMS is a collection of software programsto enable users to create, maintain andutilize a database.

Database Management Systems (DBMS)Program or set of programs designed to control access to the database manage data resources


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What is a DBMS?

DBMS

Insert records

Delete records

Update records

Query records


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What is a DBMS? Commercial DBMS

Company Product

Oracle Oracle 8i, 9i, 10g

IBM DB2, Universal Server

Microsoft Access, SQL Server

Sybase Adaptive ServerInformix Dynamic Server

1. Worlds 2nd largest softwarecompany

2. CEO, Larry Ellison, worlds 2ndrichest

Worlds 2nd largest after Informixacquisition


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What is a DBMS?

Commercial DBMS

Company Product

Oracle Oracle 8i, 9i, 10g

IBM DB2, Universal Server

Microsoft Access, SQL Server

Sybase Adaptive ServerInformix Dynamic Server

Access comes with MS Office

CEO, John Chen, grown up in HK

Acquired by IBM in 2001


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Why do we need a DBMS?

To reduce application development time

Suppose we are given a collection ofraw files which occupy 500GB

What are the drawbacks?


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Drawback of File System

1. Data Redundancy and Inconsistency

E.g., consider a bank application

address of a customer in the file of saving-accountsand

the file of checking-accounts

A good design of DBMS can avoiddata redundancy and inconsistency.


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2. Difficulty in accessing data

Need to write a new program to carry out

each new task

It is easy to obtain data with DBMS


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3. Integrity problems


The balance cannot be below $1000

The day of a month cannot exceed 31

DBMS can check the integrityautomatically


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4. Atomicity of updates


We want to transfer $100 from account A toaccount B

Steps:

Step 1: We deduct $100 from account A

Step 2:Then, we increment $100 in account B

If the system crashes at Step 1, then Step 2cannot be executed

DBMS makes sure that Step 1 and Step 2can be executed together even with acrash (We call the execution is atomic.)


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5. Concurrent Access by multiple users Uncontrolled concurrent accesses can lead to inconsistencies


There is an account shared by 2 customers A and B

Customers A and B withdraw $1000 concurrently

DBMS makes sure that the concurrentaccess cannot lead to this problem

Read 5000Read 5000

5000 - 1000

Write 4000

5000 - 1000

Write 4000

A B


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6. Security Problems


We do not want system programmers to havepermissions to read some data(e.g., Andy Laus saving account and

Joey Yungs saving account)

Need a lot of effort to re-write a programfor this permission system

DBMS can enforce that different users havedifferent permissions to access differentparts of the data


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Advantages of DBMS

With the use of DBMS, we have the followingadvantages

Data independence Efficient data access

Data integrity and security

Data administration

Concurrent access and crash recovery

Overall:Reduced application developmenttime


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ELE320

ENGR. J. SADOL 25

Data Models

A data model is a collection of tools or concepts fordescribing data, the meaning of data, data relationshipsand data constraints

Object-based logical models

Entity-Relationship Model (ER Model)

id

BorrowerCustomer Loan

Customer-name

Customer-street

Customer-cityLoan-number amount


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Data Models

Record-based Logical Models Relational Model

Main concept: relation, basically a table with rows and columns.A column is also called a fieldor attribute

Other models such as the Network Model, Hierarchical Model,

object-oriented model, objected-relational modelWe will focus on the dominant Relational model.

A description of data in terms of a data model is called a schema.


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Data Abstraction

is the process by which data and programsare defined with a representation similar in

form to its meaning (semantics), while hidingaway the implementation details.

Abstraction tries to reduce and factor outdetails so that the programmer can focus on

a few concepts at a time.

It hides certain details of how data is storedand maintained


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Levels of Data Abstraction



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Data Abstraction Conceptual Level

Physical arrangement of records by an

index tree D43389

C73334 F89328

A34455 C23444 E32399 G29021


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Data Abstraction

A view when posting the grades to all students

Views of a company with data on employees, departments,products, Payroll section:view on employees, departments, salaries Sales department:view on products, prices, sales, customers

Purchasing department:view on parts, with pricing


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Data Independence

Physical Data Independence

Change of physical database schemas

without change of conceptual databaseschemas or application programs

Logical data independence

Change of conceptual schemas withoutchange of external views


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What languages does thecomputer speak?

Data Definition Language (DDL)

A language that specifies data schemas

Data Manipulation Language (DML) A language to facilitate the retrieval, update of

data in the database

For retrieval, we query the database with thequery language, which is part of the DML


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People who deal withdatabases

Database Administrator (DBA):Person(s)who has central control over the database

and is responsible for the following tasks Schema definition/modification

Storage structure definition/modification

Authorization of data access

Integrity constraint specification Monitoring performance

Responding to changes in requirements


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People who deal withdatabases

Application Programmers Embed DML calls in program written in a host language (e.g.,

Cobol, C, Java). (DML stands for data manipulation language)

e.g., programs that generates payroll checks, transfer fundsbetween accounts

Sophisticated users Form request in database query language

Nave users Invokes one of the permanent application programs that

have been written previously

e.g. transfer transfer fund between accounts


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Structure of a DBMS

Query Optimization and Execution

Relational Operators

Files and Access Methods

Buffer Management

Disk Space Management


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History

The first generall purpose DBMS was designed byCharles Bachman at GE in early 1960s

In 1970 Codd at IBM proposed a new data

representation framework called the relational datamodel.

The SQL query for relational databases, developed aspart of IBMs System R project, was standardized inthe late 1980s.

The current standard, SQL-92, was adopted by ANSI(American National Standards Institute) and ISO(International Standards Organization).


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History

In late 1980s and 1990s, several vendors (e.g., IBMsDB2, Oracle 8) have extended their systems with theability to store new data types such as images andtext.

Specialized systems developed for datawarehouses, consolidating data from severaldatabases.Entering the Internat Age, a new markup languageXMLis proposed for data access through a Web

browser.As more and more data are collected, companies arealso interested to mineuseful information from theirdata.

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