DATABASE MANAGEMENT DATABASE MANAGEMENT SYSTEMS SYSTEMS

MJS-15

BYAbhishek & Sai Kumar

Introduction to DBMSWhat is Database?Purpose of Database SystemsFile System vs. DBMSView of DataData ModelsRDBMSDDLDMLDCLTCL

MJS-15 Index

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• A software used to manage data.• A very large, integrated collection of data.• A collection of information stored in a computer in

a systematic way.

Databases• MySql• Postgresql• Oracle

What is Database..?

Database Management System (DMBS)

Collection of interrelated dataDMBS contains information about a particular

enterpriseDBMS provides an environment that it both

convenient and efficient to use

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File System vs. DBMSadvantages disadvantages

FMS • Simpler to use• Less expensive

• Typically no multi-user access• Limited to smaller databases• Limited functionality• Decentralization of data• Redundancy and integrity issues

DBMS • Greater flexibility• Greater processing power• Ensures data integrity• Supports simultaneous access• Provides backup and recovery controls• Advanced security

• Difficult to learn• Packaged separately from the OS• Slower processing speeds• Requires skilled administrators• Expensive

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Purpose of Database Systems

Data redundancy and inconsistencyDifficulty in accessing dataData isolation – multiple files and formatsIntegrity problemsConcurrent access by multiple usersSecurity problems

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Database management systems were developed to handle the following difficulties of typical file-processing systems supported by conventional operating systems:

View of DataAn architecture for a database system

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Physicallevel

Logical level

View level

Levels of AbstractionPhysical level: describes how a record (e.g.

customer) is stored.Logical level: describes data stored in database,

and the relationships among the data.type customer = record

name: string; street: string; city: integer;end;

View level: application programs hide details of data types. Views can also hide information (e.g. salary) for security purposes.

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Instances and Schemas

Similar to types and variables in programming languagesSchema – the logical structure of the database (e.g., set

of customers and accounts and the relationship between them)

Instance – the actual content of the database at a particular point in time

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Data ModelsA collection of tools for describing:

Data relationshipsData constraints

Object-based logical modelsEntity-relationship model

Record-based logical modelsRelational model (e.g., SQL/DS, DB2)

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Entity-Relationship Model

Example of entity-relationship model

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customer accountdepositor

social-security customer-street

customer-name

account-number

balancecustomer-city

What is RDBMS..?

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• RDBMS stands for Relational Database Management System.

• RDBMS data is structured in database tables, fields and records.

• In this data will be stored in the from rows and columns.

• RDBMS also provide relational operators to manipulate the data stored into the database tables.

Relational Model

Example of tabular data in the relational model:

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name ssn street city account-numberJohnson 192-83-7465 Alma Palo Alto A-101Smith 019-28-3746 North Rye A-215Johnson 192-83-7465 Alma Palo Alto A-201Jones 321-12-3123 Main Harrison A-217Smith 019-28-3746 North Rye A-201

account-number balanceA-101 500A-201 900A-215 700A-217 750

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There are four types of query languages as follows.

•Data Definition Language (DDL)•Data Manipulation Language (DML)•Data Control Language (DCL)•Transaction Control (TCL)

RDBMS Query Languages.

Data Definition Language (DDL)A DDL is a language used to define data structures and modify data.DDL Commands:•Create•CREATE TABLE employee(empID int, Ename char(20), Esalary int, Eadd varchar(25));

•Alter•ALTER TABLE employee ADD Ecountry varchar (50);

•Drop•DROP TABLE employee;

•Truncate• TRUNCATE TABLE employee;

•Rename•SELECT Ename AS Emp_name FROM employee;

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Data Manipulation Language (DML)

A DML is a language used for managing data in database.DML Commands:•Select• SELECT * FROM employee;

•Insert•INSERT INTO employee(EmpId, Ename, Esalary, Ecity) VALUES (502 ,‘sandeep',‘25000',hyderabad' );

•Update•UPDATE employee SET Ename=‘bharath', where Ecity=hyderabd';

•Delete•DELETE FROM Employee WHERE Ename=‘sandeep‘;

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Data Control Language (DCL)

A DCL is a language used to control privilege in Database

DCL Commands:•Grant•Syntax: REVOKE [permission] ON database.table FROM 'user‘@'localhost'; Example: GRANT [write] ON [company_details].[employee] TO ‘[sandeep]’@'localhost’;

•Revoke•Syntax: REVOKE [permission ]ON database.table FROM 'user‘@'localhost'; Example: REVOKE [write] ON Company_details.Employee FROM ‘Sandeep'@'localhost';

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Transaction Control Language (TML)

A TCL is a language used to manage transactions in database

TCL Commands:•Commit : save work done•Syntax: commit

•Rollback : restore database to original since the last COMMIT•Syntax: rollback;

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Any Queries…?MJS-15 12