1. Introduction to Database Systems

Topics:

1. What is a database ?

2. Database Management System (DBMS)

3. Database Vs DBMS

4. File Managers Vs. DBMS

5. Data Models & Kinds of DBMSs

6. Database Languages

7. History of Database Systems

What is a Database ?

A database is a collection of data.

Example databases:

Attendance Register (at office reception)

Bank Accounts (in a bank)

A scroll of shopping list (in your pocket)

ColorNote Data (in your smart phone)

A bunch of resumes (on HR manager's table)

Contact list (in your smart phone)

Attendance Register is a Database

An attendance register contains at least one record for each employee.

An employee is typically expected to write a serial number, his/her name, time of entry into the office, time of exit from the office, entry-time signature and exit-time signature. One may also write purpose of entry during non-office hours and so on. The register contains multiple record entries for each day. It is essentially a collection of records or data and hence it is a database. The database is not computerized but it is maintained manually. In any case, it is a database.

A Scroll of Shopping List is a Database

Most of you must be noting list of items you need to bring from a shop or market.

For example, the list may contain items such as “1 kg Sugar, one tooth paste, two soaps,...”. This list that you may have noted on a paper is nothing but collection of data. Hence, it is a database but not in a computer. Each data item here contains name of shopping item, weight (e.g., “1 kg”) or a number (e.g., “two”) depending on the type of item.

A Bunch of Resumes is a Database

Many resumes may be lying on the table of your HR manager!

The collection of resumes is nothing but a database. Of course some may be lying on the table of the HR manager, some may be in a cup-board and yet some may be in inbox of email client program the manager uses. Each resume contains data items such as name of candidate, date of birth, qualifications, experience, etc. All these resumes can be treated as manually maintained database.

Bank Accounts in a bank is a Database

Account data maintained by bank for its customers is a database. It is a collection of data of all customers.

Banks may maintain variety of data for each customer. Not only simple and mandatory data such as name, account number and balance, banks may maintain data such as fixed deposit amount, rate of interest, amount of loan given, etc. All this data is part of the database. Nowadays all most all banks store the data in computers managed by specialized software (we are going to talk about such software later in great detail)

ColorNote notes is a Database

ColorNote is a software that runs on Android devices such as mobile phones. You can create various notes you want to remember and save them so that you can refer to them in future. For example, I use ColorNote for storing information on my bank account details, passport details, income tax details, etc., so that I can refer to them while filling various forms. All these notes, a collection of data, is nothing but a database.

Contact List is a Database

List of names persons along with their phone numbers and/or email IDs and other related data you store in your mobile phone, tablet or on your PC is also a database.

Recapitulation

Database is a collection of data.

There are manually maintained databases and computerized databases.

An example for manually maintained database is attendance register.

An example for computerized database is bank account data.

What is a Database Management System?

A database management system is a software used to create,

query, manipulate and control databases.

Short name for database management system is DBMS.

Database Management System Environment

DBMS

Database

Application

Database Database

Application Application Application

Database Creation

The creation of a database usually involves specification of a name for the database and other parameters.

Database Querying

Querying means retrieving required data from the database.

For example, you may want to retrieve “name and account number of customers” from the database.

Required means based on conditions such as “balance > $5000”.

Database Manipulation

Manipulation means

adding new data to the database

modifying existing data in the database or

deleting existing data from the database

Database Control

Control means

limiting access to data only to authorized users

sharing data among the users in such a way that database integrity is maintained

DBMS Components

Database Server

ODBC Driver

JDBC Driver

.NET Data Provider ISQL LOAD DUMP SCHEMA

REPORT

BACKUP

RESTORE

ESQL / C

ESQL / Java

MONITOR

Communication Network

Ap

plic

atio

n D

eve

lop

me

nt In

terf

ace

s

Adhoc query and manipulation tool

databases

Database Vs DBMS

A database is a collection of data.

A database usually consists of data in

one or more files on one or more disks

of a computer or it may be distributed

across multiple computers.

Database is not a software.

Database Vs DBMS

DBMS on the other hand is a software.

DBMS is used to manage databases.

DBMS usually consists of one or more

programs (executables and libraries)

written in programming languages such

as C, C++ and Java.

Database Vs DBMS

Database != DBMS

File Managers Vs DBMS

Some File managers or Storage

Managers / systems:

C-ISAM (Informix,IBM)

ObjecTrieve (Cosoft)

C-Tree (Faircom)

BerkeleyDB (Oracle)

File Managers Vs DBMS SNO Functionality File Manager DBMS

1 Retrieval of data that is a combination of data from multiple types of records

Lot of programming effort is required

Very easy to retrieve such data

2 Data security Application has to build from scratch

Basic security definition capability is built into the DBMS.

3 Changes in record structure or data types

Big impact on applications

The impact is minimal

4 Performance tuning Difficult to tune once database structure is frozen.

Tuning is much lot easier

5 Application portability Not portable Higher level DBMS APIs make applications portable across DBMSs from different vendors

6 Programming productivity

Low as the APIs are low level.

High.

Data Models & DBMSs

Data Models & DBMSs

Data model: Structure + Operations

Structure: Record structures, field data

types, lengths, keys, etc.

Operations: Retrieval, Addition,

Modification, Deletion, etc.

Categories of Data Models

Object-based Data Models

Record-based Data Models

Physical Data Models

Data Models Used by DBMSs

Main data models used by most of the

DBMS are as follows:

Network Data Model

Hierarchical Data Model

Relational Data Model

Object-Oriented Data Model

Other Data Models

Entity-Relationship Data Model

Network Data Model

Network Data Model

Introduced in the conference on Data and

Systems Language (CODASYL) in 1971.

Main Concepts: – Record Types

– Data Items

– Links

Network Data Model Database

•Database consists of records of one or more

Record Types.

•A record type defines structure of records;

number of data items and data types of items.

•Data Items are fields of record types.

•Links represent relation-ships between record

types.

Network Data Model Record Type

Record Type:

Represents structure of records to be

stored in the database.

Examples:

Item, Customer, Vendor, Employee,

Department and Project.

Network Data Model Data Items

Data items are fields of record type.

Examples:

Employee record type data items:

- eno // Employee number

- ename // Empoyee name

- dno // Employee dept. number

… Department record type data items: - dno // Department number - dname // Department name. …

Network Data Model Links

Links represent relationships between record types.

Graphically each record type is represented using a rectangle

with name of the record type inside it.

Links are represented by drawing an arc from one record type

to another as shown below:

Employee

Department

consists-of

The relationship name of the link is consists-of. One way to read the diagram is as follows: A Department consist of Employees.

Network Data Model Link/Relationship Types

Relationships in this model can be of two types : Binary type or

Many to one

Employee Department Employee Resume

Binary relationship Many-to-one relationship

Logical Structure of Network Data Model Database

The logical structure is represented by one or more record

types and links between them.

Each many-to-many relationship is broken into two many-to-

one relationship.

Logical structure of an example database is as follows:

Employee

Resume

is-submitted-by

Department

works-in

EmpProj Project executes executed-by

Record Type EmpProj is a dummy record type used to resolve many-to-may relationship between Employee and Project record type.

Network Data Model Based Database Management Systems

The most widely used Network DBMS is IDMS/R from

Computer Associates.

Another system is ADMIN from CMC Ltd.

Hierarchical Data Model

Hierarchical Data Model

Data is in collections of records.

Relationships are represented as sets.

A restricted type of Network Data Model.

Each Record Type can have only one Parent and thus hierarchy.

Model can be represented as a tree graph.

Record Types are nodes of the graph.

Links are edges in the graph.

Logical Structure of Hierarchical Data Model Database

Employee

Resume

Department

Project

Hierarchical Data Model Based Database Management Systems

•There are not many hierarchical database systems.

•The most widely used hierarchical database management systems is IMS (Information Management System) from IBM.

Relational Data Model

Relational Data Model

Has strong mathematical foundations

Based on the concept of mathematical relations

Data and relationships are represented using tables.

Data items are represented as columns of tables.

A relational data model based database consists of one or more tables.

Databases based on relation data model are called Relational Databases.

The data model is only a logical model. Physical data model of a DBMS could be same or different.

Logical Structure Relational Data Database

Employees Eno Ename Dno

Resumes Eno ResumeText

Departments Dname Dno Mno Projects

Pno Pname Eno Pmgr

The sample database consists of the following four tables:

Names of the columns are given below each table name.

Relational Data Database With Sample Data

Table: Employees

Table: Resumes

Table: Departments

Table: Projects

dno dname mno

1 R & D 1001

2 Marketing 1002

3 Admin 1004

eno ename eno

1001 Bhaskar 1

1002 Dinesh 2

1003 Sagar 1

1004 Harish 3

1005 Bose 1

1006 Praveen 1

eno resume_text

1001 ....

1002 ....

1003 ....

1004 ...

1005 ...

1006 ...

pno pname mno

101 LifeStyle 1005

201 ScoreWell 1003

Relational Database Terminology

General Academic

Table Relation

Column Attribute

Row Tuple

There are two kinds of terms used to refer to the same concept. Most popular are general terms compared to academic terms.:

Relational Database Management System Products

There are many relational database management systems – paid ones as well as free ones. Here are the most used relational DBMSs or RDBMSs: Oracle Database (from Oracle) MS SQL Server (from Microsoft) DB2 (from IBM) SyBase (from SAP) C-treeACE(from Faircom) MySQL (from Oracle) PostgreSQL (free) SQLite (free)

Database Languages

What you will learn from this session:

Purpose of database languages

Usage Scenarios

Components of a Database language

Database Languages

SQL - Structured Query Language

Database Languages

Database Languages Purpose

The purpose of a data language is

to communicate with DBMS to retrieve data from the database,

add data to the database, modify data in the database or delete data from the database.

Database Languages Usage Scenario -Tools

DBMS

Databases

Database Language commands

ISQL tool Results

(mysql/sqlcmd/sqlite/ sqlplus/isql/…)

Database Languages MySQL Command-Line Tool

Database Languages Usage Scenario - Applications

DBMS

Databases

Database Language

Application Results

Database Language Components

A database language consists of essentially three components each serving a specific purpose. These are as follows: Data Definition Language (DDL)

Data Manipulation Language (DML)

Data Control Language (DCL)

These languages are called data sub-languages because they do not have all constructs required for writing general programs that can be written using languages such as C, C++ and Java.

Data Definition Language (DDL)

DDL is used to define database structure. It contains various statements to define structures to hold data of specific record types or object types, relationships among them and any integrity constraints the data has to satisfy. An example DDL statement in SQL is as follows:

CREATE TABLE customers(id INTEGER, name

VARCHAR(50), address VARCHAR(200));

This statement creates a structure for a table called customers which has columns id, name and address for an RDBMS database.

Data Manipulation Language (DML)

DML is used to retrieve data from the database, add data to the database, modify existing data in the database or delete data from the database. The part of DML used to retrieve data is called Query language. An example DML statement for adding data is as follows:

INSERT INTO customers VALUES(1, 'Akhil', '305, 2nd C

Main Road, 8th Block, Koramangala, Bangalore - 560095');

Note! Terms DML and Query language are used interchangeably.

Data Control Language (DCL)

DCL is used to control access to data. Controlling data access primarily involves giving privileges to users to access data items, or taking away privileges from the users who do not need them and transaction management. An example for giving privilege on a table to a user in SQL is as follows:

GRANT SELECT ON customers TO praveen;

Database Languages

There are not many languages proposed as such unlike

regular programming languages. Some of the languages

implemented by database products are as follows:

SQL – Structured Query Language

QUEL – Query Language

QBE – Query By Example

Database Languages Structured Query Language (SQL)

Structured Query Language or SQL is the most widely

implemented and used language for relational database

management systems.

SQL covers DDL, DML and DCL. There is an international standard for the language. Defined by D.Chamberlin of IBM in 1974 as SEQUEL (Structured English Query Language). A revised version called SEQUEL/2 was defined in 1976 and the name was changed to SQL for legal reasons.

Database Languages Query Language - QUEL

QUEL is the query of language of relational database management systems INGRES and SPREADS. QUEL was overshadowed by SQL and hence its user base is almost nil. An example query is: RANGE OF e IS employees RETRIEVE (e.ename) WHERE e.salary > 5000

Database Languages Query By Example (QBE)

QBE is one of the first graphical user interfaces.

Developed by IBM and is available as part of QMF (Query

management Facility) interface of DB2.

QBE is available for Microsoft Access DBMS as well. No rigid syntax, no need to remember table names and column names. QBE can be used for data definition as well.

History of

Database Systems

History of Database Systems

SNO YEAR Historical Information

1 1961 Bachman introduced the concept of record and set types. Database Task Group (DBTG) used the concept to develop CODASYL Network Data Model.

2 1964 The first DBMS called Integrated Data Store was designed by Backman for GE.

3 1965-70 IBM introduced Hierarchical Model and developed DBMS called Information Management System (IMS). Commerical DBMSs emerged: IDMS (Computer Associates), IDS II (Honeywell), DMS 1100 (UNIVAC's), DMS-170 (CDC), DBMS-11 (DEC) and PHOLAS (Phillips)

4 1970 Relational Data Model was introduced by Ted Codd of IBM.

5 1971-76 Many research activities were initiated in the area of database systems. Chen introduced E-R Model.

History of Database Systems

SNO YEAR Historical Information

6 1976 RDBMSs developed: System R (IBM), INGRES (Univ. of California, Berkeley), System 2000 (Univ. of Texas, Austin), ADABAS (Tech. Univ. of Darmstadt), DB2 and SQL/DS (IBM), Oracle (Oracle Corp) Query Languages developed: ISBL, SQUARE, SEQUEL, QBE, QUEL, SQL, ...

7 1984 - DBMSs were enhanced with various tools for report generation, graphical diagrams, etc. Indian companies also came with relational database managements systems SPREADS (CMC), ADMIN (CMC), Integra4 (COSOFT) and Dharma/SQL Access (Dharma Systems).