dbms

Overview of Database Management Systems

Objectives & Role

Advantages & Disadvantages of DBMS

SQL

Uses of Database for Integration across Functional Areas

Database Applications

• In most organizations the data files tend to grow In most organizations the data files tend to grow independentlyindependently

• Accounting, HR, Marketing, Manufacturing etc, all Accounting, HR, Marketing, Manufacturing etc, all departments end-up developing their own departments end-up developing their own independent systems and data filesindependent systems and data files

e.g. e.g. • HR dept may have a master file containing payroll file, HR dept may have a master file containing payroll file,

employee insurance file, pension fileemployee insurance file, pension file• At the same time Accounting dept may also have the same At the same time Accounting dept may also have the same

filesfilesMany files in organizationMany files in organizationDifficult to manageDifficult to manageWastage of resourcesWastage of resources

• Many businesses often do not haveMany businesses often do not have

- - timelytimely

- accurate- accurate- or relevant information- or relevant information- because of poorly organized data- because of poorly organized data

This is why the database management systems are so This is why the database management systems are so essentialessential

We will be discussing the roles/ benefits of Database We will be discussing the roles/ benefits of Database Management Systems in the later sessionsManagement Systems in the later sessions

Track information Keep consistent standards Allow higher productivity as a

result of better information

A structured collection of related data An filing cabinet, an address book, a

telephone directory, a timetable, etc. Google and your email is a database School Student Information System

Database System

A database, a database management system and appropriate hardware and personnel.

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number, Designati

onHours

worked, Pay rate

Insurance, Pension

Database Management SystemSystems software that facilitates the

management of a database.

E.g. Oracle, Access, SQL Server

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DBMS An application software that organises

data into records in one or more databases and allows organising, accessing and sorting of the data in a variety of formats.

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• Bit

• Byte

• Field▫ Smallest meaningful unit of data▫ Group of one or more characters that has a specific meaning

• Record▫ Set of fields containing all information known about one

entity▫ Each record contains the same fields in the same sequence

• File▫ Collection of related records

TableName: Barry HarrisCollege: MedicineTel: 392-5555

Name: Barry HarrisCollege: MedicineTel: 392-5555

Name: Barry Harris

Field

Record

Records

Fields

Name GatorLink Phone College

Graff rgraff 392-3900 Pharmacy

Harris bharris 392-5555 Medicine

Ipswich zipswich 846-5656 PHHP

Four components: People, H/W, S/W, Data Practitioners (analysts and database

designers) in consultation with users identify data needs and design database structures to accommodate these needs.

The database structures are specified to the DBMS through the data dictionary.

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•Users enter data into the system by following specified procedures.

•The entered data are maintained on hardware media such as disks and tapes.

•Application programmes that access the database are written by practitioners and users to be run on computers.

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DATABASE

DATA DICTIONAR

Y/ DIRECTORYUSER

PROGRAMMER

Data Dictionary/ Directory

SubsystemSecurity and

Integrity SubsystemDatabase

Access Subsystem

User Query and Reporting

Facilities

Application Program

Development Facilities

DBMS

USER

PROGRAMMER

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DATABASE

DATA DICTIONAR

Y/ DIRECTORY

Application Program

Application Program

Application Program

DBMS

ComputerTerminals

PRINTER

Analyst

User

Set of physical devices on which a database resides. It consists of one or more computers, disk drives, CRT terminals, printers, tape drives, connecting cables and other auxiliary and connecting hardware.

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Client

Client

Server

TAPETAPEPrinter

A database software includes two types of softwareGeneral-purpose database management

software like operating system.Application software that uses DBMS

facilities to manipulate the database to achieve a specific business function, such as providing reports or documents, which can be used by users.

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•Application software is generally written standard programming language such as C, or it may be written in a language (commonly called a fourth-generation language) supplied with the DBMS.

•These programs utilise the command language of the DBMS and make use of the information contained in the data dictionary.

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• User Interface▫ Language, menus and other facilities by which

users interact with various system components, such as application programs, the DBMS

• Computer-aided software engineering (CASE) tools▫ Automated tools used to design databases and

application programs.

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A subsystem that keeps track of thedefinitions of all data items in the

database. relationships that exists between

various data structures. indexes that are used to access data

quickly.screen and report format definitions that

may be used by various application programs.

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Definitions of data items in the database includes:

Elementary-level data items (fields), group and record-level data

structures, andfiles or relational tables.

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• Data that describe the properties or characteristics of other data.

• Some of these properties include data definitions, data structures and rules or constraints. Item name, the data type, length, minimum and maximum allowable values (where appropriate) and a brief description of each data item.

• Metadata allow database designers and users to understand what data exist, what the data mean.

• Data without clear meaning can be confusing, misinterpreted or erroneous.

Metadata

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E.g. Data Item ValueName Type Length Min Max

DescriptionName Character 30 Employee NameID Number 9 Employee No.Dept Character 10 Dept. No.Age Integer 2 18 60 Employee Age

Name Character 15 Dept. NameManager Number 9 Mgr. Emp. No.

Employee No. (ID) uniqueManager is an employee of the organisation

Metadata

Two different types of people (users and practitioners) are concerned with the database.

Userswho need information from the

database to carry out their primary business responsibility

e.g. Executives, managers, staff, clerical personnel

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Practitioners▫people responsible for the

database system and its associated application software.

e.g. Database administrators, analysts, programmers, database and system designers, information systems managers.

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Database Applications:Banking: all transactionsAirlines: reservations, schedulesUniversities: registration, gradesSales: customers, products, purchasesManufacturing: production, inventory,

orders, supply chainHuman resources: employee records,

salaries, tax deductions Databases touch all aspects of our lives

The database is a valuable resource needing protection.

The DBMS provides database security by limiting access to the database to authorised personnel.

Authorised users will generally be restricted as to the particular data they can access and whether they can update it.

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Access is often controlled by passwords and by data views, which are definitions of restricted portions of the database.

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1

Data items

234

The integrity and consistency of the database are protected via constraints on values that data items can have and by backup and recovery capabilities provided within the DBMS.

Data constraint definitions are maintained in the data dictionary.

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Backup and recovery are supported by software that automatically logs changes to the database and provides for a means of recovering the current state of the database in case of system failure.

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One of the chief functions of the DBMS is to support the access, retrieval and update of data in the database.

The DBMS provides the physical mechanisms allowing multiple users to access a variety of related data quickly and efficiently.

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DBMS provides user-oriented data manipulation tools.

Easy-to-use query languages allow users to formulate queries and request one-time reports directly from the database.

Often query languages will contain facilities to format the results of queries as reports.

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Capabilities vary considerable, but basic operations are:

Data definition Data entry Data manipulation Data display

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Database TypesRelationalObject-orientedHierarchical

Each type structures, organizes and uses data differently

Hierarchical relationships among different types of data.

Can be very easy to answer some questions, but very difficult to answer others

If one-to-many relationship is violated (e.g., a patient can have more than one physician) then the hierarchy becomes a network

Root

1st Child

2nd Child

EMPLOYEEoIdoDeptoPositionoAddress

COMPENSATIONADDITIONAL

BENEFITS

HEALTH INSURANCE

PERFORMANCE RATING

SALARY HISTORY

•Data are organized as logically independent tables

•Not so strongly biased towards specific questions

•Expresses relationships by means of shared data rather than explicit pointers

•Theoretical basis: relational algebra, calculus; closure

•Operations on tables (Join, Project, Select) to form new tables

Object-oriented analysis is another way to model the world, involving abstraction, encapsulation, modularity and hierarchy (with inheritance).

An object consists of data and methods. Classes are used to group objects which

have the same types of data and the same methods.

Data Warehouses Data Marts OLAP (Online Analytical Processing)

Data Mining

Data Warehouseso It is hard to gather data from different

departmentso Data Warehouse stores the current and historical

data throughout the companyo This data originates from different TPS such as

Sales, Finance, HR etco Data Warehouse consolidates and standardize the

information gathered from different operations databases

o This information is further used for management analysis and decision making

Data Martso Smaller Data Warehouses or Subset of Data

Warehouseo For specific population of users

OLAPo Supports multidimensional data analysis i.e. enables

users to view the same data in various ways using multiple dimensions

o Enables users to obtain online answers to ad-hoc questions

Data Miningo More discovery-driven i.e. provides insights into

organization data that can not be obtained by OLAPo Patterns and rules are used to guide decision making or

forecasting the effects

Example:A supermarket data tells that Coca-Cola is purchased 65%

of the time, but whenever there is special sale on Coca-Cola, the figure goes to 85%.

How to project or analyze the overall profitability from different types of special sale? (what-if analysis)

How can we analyze the group of items e.g. people buying Coca-Cola and Chips at the same time?

• Data independence

•Application programs should not, ideally, be exposed to details of data representation and storage.

• Efficient Data access

•A DBMS uses several powerful functions to store and retrieve data efficiently

•Data Integrity and Security

•The DBMS enforces integrity constraints to get a kind of protection against prohibited access to data.

• Data Administration

When any users share the data, centralizing the administration of data can offer significant improvements.

• Concurrent Access and Crash Recovery

A DBMS schedules concurrent access to the data in such manner that users can think of the data as being accessed by only one user at a time. DBMS also protects users from the effects of system failures.

• Reduced Application Development Time

DBMS includes several important functions that are common to many applications accessing data in the DBMS. In conjunction with the high-level interface to the data, facilitates quick application development.

a. Complexityb. Sizec. Technical experts are required d. Cost of DBMS development e. Additional hardware costsf. Performance monitoring & maintenance g. Higher impact of a failureh. Centralization: That is use of the same program

at a time by many user sometimes lead to loss of some data

i. Limited Statistical Capabilities: Can not perform sophisticated calculations Security issues

Most of the times managers deal with the databases created by someone else, therefore, as a manager you must know how to retrieve the required data

SQL: is an international standard method for retrieving data from the DBMS

Standard Language: supported by various types of database systems, so the commands will work same in various situations

Readability: easy to read just like ordinary English Reusability: SQL consists of blocks of code which

can be stored in the database and reused Error Handling: contains error handles errors that

track the errors or exceptions during execution. Once an error or exception is caught, specific actions can be taken depending upon the type of the exception or it can be displayed to the user with a message

Better Performance: multiple SQL statements simultaneously as a single block, thereby reducing network traffic

High speed: SQL queries are designed to retrieve large amounts of records from a database quickly and efficiently. With the help of simple SQL queries, you can retrieve even highly complicated combination of data from the database

Security: With the SQL database storage, you get the security of all the data being in one place, which you can manage easier.

Coding: SQL is moderately complex. There are only few commands but each command can have several interweaved components. Therefore, it is difficult to learn

Incapable of performing sophisticated calculations: Can only perform simple calculations

Difficulty in interfacing : Since an SQL database supports many advanced features, interfacing to an SQL database is more difficult than just adding a few lines of code