Management Information Systems

Lection 03Database management system

CLARK UNIVERSITY

College of Professional and Continuing Education (COPACE)

Plan

• Term “Database”• Architecture of database• Data models• Normal forms• Operations of relation algebra• Operations of SQL• DBMS

Term “Database”

• A huge amount of data is entered into computer systems every day.

• Where does this data go and how is it used?• How can it help you on a job?

Term “Database”

Widely database is a collection of facts about real world’s objects if some field.

Field is a part of the real world which we learn for managing: company, university, etc.

Non-structured data

Folder No. 16493, Smith John, 01/01/1976; folder No. 16593, LeVering Barbara, 03/15/1975; folder No. 16693, McCow Robert, 04/14/1976.

Structured data

Structuring is the introduction of agreements on the ways of presenting data.

Folder No. Surname First name Birth date

16493 Smith John 01/01/1976

16593 LeVering Barbara 03/15/1975

16693 McCow Robert 04/14/1976

Database definition

• Database (DB) is a named collection of structured data related to a particular subject area.

• Database management system (DBMS) - a set of software and language tools necessary to create databases, keeping them up to date and organize the search in them the necessary information.

Classification of databases

Centralized

stored in a computer system, which may be the mainframe (access

via terminals) or file server network.

Data processing

Distributedconsists of several parts, which are

stored in different computer network

connection.

Classification of databases

With local access

Access to data

With network access

Classification of databases

Centralized database with network access can have the following architecture:

File-server Client-server Two-level model Three-level model

Architecture “File-level”

1. Input and Display data

3. Implementation of computing functions on the data

2. Data access and search Criteria

1. Keeping the database file

АрхитектArchitecture “File-level”ура файл-сервер

1. The absence of very high performance of the server (most importantly - the required amount of disk space)

2. The database is not running and will not being installed on a server

1. High network traffic

2. Lack of special security arrangements file from the DB

Advantages:

Disadvantages:

АрхитектArchitecture “File-level”ура файл-сервер

Architecture “Client-server”

1. Input and display data2. Implementation of computing functions on data sets

1. Keeping the database file2. Access to the data and

search for certain criteria

Architecture “Client-server”

1. Lower network traffic than the file-server model 2. SQL-Server provides functions to ensure the integrity and security of data

1. In certain cases, some data sets may take quite a substantial amount of place

Advantages:

Disadvantages:

Architecture “Client-server”

1. Input and Display data1. Keeping the database file2. Data access and search by

criteria3. Implementation of computing

procedures on data sets

Two-level architecture

Advantages:

Disadvantages:

1. High demands on the computer server (disk space and speed)

Two-level architecture

1. Significant reduction in network traffic compared to client server 2. High reliability of data storage and processing

Three-level architecture suggest the following application components: a client application ("thin client" or a terminal) connected to the application server, which in turn is connected to the database server.

Three-level architecture

Stored data have a logical structure described by a model of data (data model), supported by the DBMS.

Data model determines the organization of data, constraints and the set of operations that are allowed on the object.

Data models

Hierarchical model Network model Relational model

Data models

The hierarchical model has been developed historically in the first turn. Based on this model it was created the first professional DBMS IMS in the late 60's - early 70‘s (IBM).

Hierarchical model

Links between different entities of data are described by a structured graph or a tree

Hierarchical model

1. Sufficiently high run-time operations on data

1. Complexity of understanding for the average user 2. The presence of redundancy

Advantage:

Disadvantages:

Hierarchical model

Link between the data are described by an arbitrary graph

Network model

1. Minimum redundancy2. Compared to the hierarchical model the network model provides

a great deal in terms of the admissibility of the formation of new links

3. Effective implementation in terms of memory consumption.

1. Complexity of understanding for the average user 2. Weakened control of the accuracy of links

Advantages:

Disadvantages:

Network model

The relational model was proposed by Edgar Cod in 1970.

Based on the concept of relation.

Graphically represented as a ratio of a table.

In a relational database assumes that the user perceives the database as tables.

Relational model

Relational modelFolder No. Surname First name Birth date Group

16493 Smith John 01/01/1976 111

16593 LeVering Barbara 03/15/1975 111

16693 McCow Robert 04/14/1976 112

1. Simplicity and clarity for a wide user, which is the reason of its wide distribution.

1. Necessary redundancy because of the relationships between tables.

Advantage:

Disadvantage:

Relational model

There are alternatives to the terms:

Relational model

Alternative 1 Alternative 1 Alternative 1

Table File Relation

String Record Tuple

Column Field Domain

Primary key

Primary key is a relation attribute (set of attributes) that uniquely identifies each of its records. Student (FolderNo., Surname, First_name, Birth_date, Group)

Folder No. Surname First name Birth date Group

16493 Smith John 01/01/1976 111

16593 LeVering Barbara 03/15/1975 112

16693 McCow Robert 04/14/1976 113

Foreign keyWe can link tables by foreign keys.

Foreign key is an attribute (set of attributes) of relation, which is the key of another relation.

Student(FolderNo., Surname, First_name, Birth_date, Group)Group(Number, Specialisation, Head_of_group)

Indexes

Index is a means to accelerate the search operation records in the table, as well as other operations that use search (retrieval, modification, sorting, etc.)Surname Location Location … Surname

Alekseev 1 1 Alekseev

Afanasiev 4 2 Yakovlev

Kuznecov 1000 3 Mikhailov

Mikhailov 3 4 Afanasiev

… …

Yakovlev 2 1000 Kuznecov

Types of indexes

Primary

The key field is always indexed, so it doesn’t require an additional

index.

Indexes

Secondary

• The are used for enforcing searching and executing

queries• There might be several

secondary indexes• They might include several

fields• The same field can enter

different indexes

Data redundancy

Folder No. Surname First name Birth date Group Specialization

15345 Ivanov Ivan 04/15/1989 392 Informatics and Management

15349 Medvedeva Anna 02/13/1989 392 Informatics and Management

15310 Petrov Mikhail 11/12/1989 392 Informatics and Management

15259 Sidorov Nicolay 01/26/1987 591 Informatics and English

15263 Sanin Alexander 10/20/1987 591 Informatics and English

The problem of update Folder

No.Surna

meFirst

nameBirth date

Group

Specialization

Term Course Score

15345 Ivanov Ivan 04/15/1989

492 IM 2 English Good

15345 Ivanov Ivan 04/15/1989

492 IM 2 Theory of algorithms

Excellent

15345 Ivanov Ivan 04/15/1989

392 ?

IM 2 Chemistry Good

15310 Petrov Mikhail 11/12/1989

392 IM 6 English Satisfactory

15310 Petrov Mikhail 11/12/1989

392 IM 6 Theory of algorithms

Satisfactory

15310 Petrov Mikhail 11/12/1989

392 IM 6 Chemistry Good

15259 Sidorov Nicolay 01/26/1987

591 IE 10 Architecture of PC

Excellent

15259 Sidorov Nicolay 01/26/1987

591 IE 10 Computer modeling

Excellent

The problem of inserting new data Folder

No.Surname First

nameBirth date

Group Speciali-zation

Term Course Score

15345 Ivanov Ivan 04/15/1989

392 IM 2 English Good

15345 Ivanov Ivan 04/15/1989

392 IM 2 Theory of algorithms

Excellent

15345 Ivanov Ivan 04/15/1989

392 IM 2 Chemistry Good

15310 Petrov Mikhail 11/12/1989

392 IM 6 English Satisfactory

15310 Petrov Mikhail 11/12/1989

392 IM 6 Theory of algorithms

Satisfactory

15310 Petrov Mikhail 11/12/1989

392 IM 6 Chemistry Good

15259 Sidorov Nicolay 01/26/1987

591 IE 10 Architecture of PC

Excellent

15259 Sidorov Nicolay 01/26/1987

591 IE 10 Computer modeling

Excellent

15402 Stepanov Andrew 03/29/1991

191 MSIT 1 - -

Нормализация

The normalization of relations represent rules of such formation of relations (tables) that allow to eliminate duplication, inconsistency stored in the database.

E. Codd developed three normal forms of relations and the mechanism, which allows to convert any relation to the third normal form.

Нормализация

Первая нормальная форма (1НФ)

Table is in 1NF if each its cell has always the only atomic value, and there can never be the set of such values.

The table is not in 1NF

Первая нормальная форма (1НФ)

Folder No.

Surname First name

Birth date

Group Speciali-zation

Term Course Score

15345 Ivanov Ivan 04/15/1989

392 IM 2 English Good

Theory of algorithms

Excellent

Chemistry Good

15310 Petrov Mikhail 11/12/1989

392 IM 6 English Satisfactory

Theory of algorithms

Satisfactory

Chemistry Good

15259 Sidorov Nicolay 01/26/1987

591 IE 10 Architecture of PC

Excellent

Computer modeling

Excellent

Table is in 1NF

Первая нормальная форма (1НФ)

Folder No.

Surname First name

Birth date

Group Speciali-zation

Term Course Score

15345 Ivanov Ivan 04/15/1989

392 IM 2 English Good

15345 Ivanov Ivan 04/15/1989

392 IM 2 Theory of algorithms

Excellent

15345 Ivanov Ivan 04/15/1989

392 IM 2 Chemistry Good

15310 Petrov Mikhail 11/12/1989

392 IM 6 English Satisfactory

15310 Petrov Mikhail 11/12/1989

392 IM 6 Theory of algorithms

Satisfactory

15310 Petrov Mikhail 11/12/1989

392 IM 6 Chemistry Good

15259 Sidorov Nicolay 01/26/1987

591 IE 10 Architecture of PC

Excellent

15259 Sidorov Nicolay 01/26/1987

591 IE 10 Computer modeling

Excellent

Диаграмма функциональных зависимостей для примера БД

«Студент»

Table is in 2NF if it does not contain any non-key attributes which are functionally dependent on part of the key

45

Table is in 3NF if it does not contain any non-key attributes, transitively dependent on the key part

Результат проектирования БД

«Студент»

Folder No.

Surname First name

Birth date

Group

15345 Ivanov Ivan 04/15/1989

392

15310 Petrov Mikhail 11/12/1989

392

15259 Sidorov Nicolay 01/26/1987

591

Group Speciali-zation

392 IM

591 IE

Folder No. Term Course Score

15345 2 English Good

15345 2 Theory of algorithms Excellent

15345 2 Chemistry Good

15310 6 English Satisfactory

15310 6 Theory of algorithms Satisfactory

15310 6 Chemistry Good

15259 10 Architecture of PC Excellent

15259 10 Computer modeling Excellent

SQL

A query language SQL (Structured Query Language) provides an access to information contained in relational databases for users, software and computing systems

Relational algebra

SQL is based on relational algebra operations. Relational Algebra is a set of operations on relations. Relational algebra was developed within the relational model by Codd.Using the relational algebra we can get other relations

Relational algebra

UnionNo. Surname Name Birth date Group

15345 Ivanov Ivan 04/15/1989 392

15349 Medvedeva Anna 02/13/1989 392

15310 Petrov Mikhail 11/12/1989 392

No. Surname Name Birth date Group

15259 Sidorov Nikolay 01/26/1987 591

15263 Sanin Alexander 10/20/1987 591

No. Surname Name Birth date Group

15345 Ivanov Ivan 04/15/1989 392

15349 Medvedeva Anna 02/13/1989 392

15310 Petrov Mikhail 11/12/1989 392

15259 Sidorov Nikolay 01/26/1987 591

15263 Sanin Alexander 10/20/1987 591

Students of group 392

Students of group 591

Result

Intersection

Relational algebra

No. Surname Name Birth date Group

15345 Ivanov Ivan 04/15/1989 392

15349 Medvedeva Anna 02/13/1989 392

15310 Petrov Mikhail 11/12/1989 392

15259 Sidorov Nikolay 01/26/1987 591

15263 Sanin Alexander 10/20/1987 591

Students of groups 392 and 591

No. Surname Name Birth date Group

15345 Ivanov Ivan 04/15/1989 392

15349 Medvedeva Anna 02/13/1989 392

15310 Petrov Mikhail 11/12/1989 392

Students of group 392

ResultNo. Surname Name Birth date Group

15345 Ivanov Ivan 04/15/1989 392

Substraction

Relational algebraNo. Surname Name Birth date Group

15345 Ivanov Ivan 04/15/1989 392

15349 Medvedeva Anna 02/13/1989 392

15310 Petrov Mikhail 11/12/1989 392

15259 Sidorov Nikolay 01/26/1987 591

15263 Sanin Alexander 10/20/1987 591

Students of groups 392 and 591

No. Surname Name Birth date Group

15345 Ivanov Ivan 04/15/1989 392

15349 Medvedeva Anna 02/13/1989 392

15310 Petrov Mikhail 11/12/1989 392

Students of group 392

ResultNo. Surname Name Birth date Group

15349 Medvedeva Anna 02/13/1989 392

15310 Petrov Mikhail 11/12/1989 392

15259 Sidorov Nikolay 01/26/1987 591

15263 Sanin Alexander 10/20/1987 591

Selection

Relational algebra

No. Surname Name Birth date Group15345 Ivanov Ivan 04/15/1989 392

15349 Medvedeva Anna 02/13/1989 392

15310 Petrov Mikhail 11/12/1989 392

15259 Sidorov Nikolay 01/26/1987 591

15263 Sanin Alexander 10/20/1987 591

Students of groups 392 and 591

No. Surname Name Birth date Group

15259 Sidorov Nikolay 01/26/1987 591

15263 Sanin Alexander 10/20/1987 591

Students of group 591

SELECT – chooseDISTINC – eliminate the same strings in the output fileFROM – from which tablesWHERE – where if condition is trueGROUP BY – grouping strings by some fieldHAVING – grouping under some conditionОRDER BY – sorting

SELECT [DISTINC] elementsFROM table(s)[WHERE condition][GROUP BY field(s) [HAVING condition]][ORDER BY field(s)]

SQL

SELECT Surname FROM Students

Select surnames of all students

No. Surname Name Birth date Group15345 Ivanov Ivan 04/15/1989 392

15349 Medvedeva Anna 02/13/1989 392

15310 Petrov Mikhail 11/12/1989 392

15259 Sidorov Nikolay 01/26/1987 591

15263 Sanin Alexander 10/20/1987 591

Students

SurnameIvanov

Medvedeva

Petrov

Sidorov

Sanin

SELECT * FROM Students WHERE Group=591

ORDER BY Surname

Select all information about students of group 591, sorting them by surname

No. Surname Name Birth date Group15345 Ivanov Ivan 04/15/1989 392

15349 Medvedeva Anna 02/13/1989 392

15310 Petrov Mikhail 11/12/1989 392

15259 Sidorov Nikolay 01/26/1987 591

15263 Sanin Alexander 10/20/1987 591

Students

No. Surname Name Birth date Group15263 Sanin Alexander 10/20/1987 591

15259 Sidorov Nikolay 01/26/1987 591

Result

SELECT Birth Date FROM Students WHERE Surname=“Petrov”

Select birth date of Petrov

No. Surname Name Birth date Group15345 Ivanov Ivan 04/15/1989 392

15349 Medvedeva Anna 02/13/1989 392

15310 Petrov Mikhail 11/12/1989 392

15259 Sidorov Nikolay 01/26/1987 591

15263 Sanin Alexander 10/20/1987 591

Students

Birth date11/12/1989

DBMSDatabase management system (DBMS) is a set of software and language tools necessary to create databases, keeping them up to date and organize the search the necessary information.

The term "database server" is generally used to refer to the entire database, based on the "client-server", including the server and client side.

Types of DBMS

Network DBMS (CronosPlus)Hierarchical DBMS (IMS)Rational (MS Access, Paradox, Interbase, FireBird,

MySQL, Oracle, Ingres)Onject-oriented and object-rational (Oracle Database,

MicroSoft SQL Server)