Mis Management Information Systems

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• View of Data • Data Models

Chapter 1: Introduction

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• Purpose of Database Systems

• Data Definition Language • Data Manipulation Language • Transaction Management

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• Storage Management • Database Administrator • Database Users • Overall System Structure
1.1 Silberschatz, Korth and Sudarshan c 1997

Database Systems Concepts

Database Management System (DBMS)

• Collection of interrelated data • Set of programs to access the data • DBMS contains information about a particular enterprise • DBMS provides an environment that it both convenient and efficient to use

Database Systems Concepts

1.2

Silberschatz, Korth and Sudarshan c 1997

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Purpose of Database Systems

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Database management systems were developed to handle the following difficulties of typical file-processing systems supported by conventional operating systems. • Data redundancy and inconsistency • Difficulty in accessing data • Data isolation – multiple files and formats • Integrity problems • Atomicity of updates • Concurrent access by multiple users • Security problems

Database Systems Concepts

1.3

Silberschatz, Korth and Sudarshan c 1997

View of Data

An architecture for a database system

view level

view 1

view 2

…

view n

logical level

physical level

Database Systems Concepts

1.4

Silberschatz, Korth and Sudarshan c 1997

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Levels of Abstraction

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• Physical 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.
1.5 Silberschatz, Korth and Sudarshan c 1997

Database Systems Concepts

Instances and Schemas

• Similar to types and variables in programming languages •