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DATABASE MANAGEMENT SYSTEMS. BASIC CONCEPTS 1. What is a database? A database is a collection of data which can be used: alone, or combined / related to other data to provide answers to the user’s question. N. Fenmen - CAA292 Database Applications for Business - 2003 - 2004 Spring.

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database management systems

DATABASE MANAGEMENT SYSTEMS

BASIC CONCEPTS

1. What is a database?

A database is a collection of data which can be used:

alone, or

combined / related to other data

to provide answers to the user’s question.

N. Fenmen - CAA292 Database Applications for Business - 2003 - 2004 Spring

database management systems2

DATABASE MANAGEMENT SYSTEMS

2. What is a Database Management System?

A DBMS is a collection of programs which

provide management of databases

control access to data

contain a query language to retrieve information easily

N. Fenmen - CAA292 Database Applications for Business - 2003 - 2004 Spring

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DATABASE MANAGEMENT SYSTEMS

3. Database Design

It is important to design the database in such a way that:

A specific item can be reached easily (maximum guarantee that the desired record will be reached)

The database can respond to the user’s different questions easily (necessary relationships are provided)

N. Fenmen - CAA292 Database Applications for Business - 2003 - 2004 Spring

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DATABASE MANAGEMENT SYSTEMS

The database occupies minimum storage space(choosing data types and how to express a certain concept is important)

The database contains no unnecessary data(storing the gross salary is enough, the net salary can be calculated from the gross salary)

Data can be added and updated easily without causing mistakes (no data redundancy)

N. Fenmen - CAA292 Database Applications for Business - 2003 - 2004 Spring

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DATABASE MANAGEMENT SYSTEMS

Data redundancy

Different and conflicting versions of the same data

e.g. Employee database:personal infopayroll

- ID - ID (relating parameter)

- name - name (causes redundancy)

- address - gross salary

N. Fenmen - CAA292 Database Applications for Business - 2003 - 2004 Spring

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DATABASE MANAGEMENT SYSTEMS

STEPS IN DATABASE DESIGN

Requirement analysis What does the user want?

Conceptual database designDefining the entities and attributes, and the relationships between these --> The ER model

Physical database designImplementation of the conceptual design using a Database Management System

N. Fenmen - CAA292 Database Applications for Business - 2003 - 2004 Spring

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DATABASE MANAGEMENT SYSTEMS

TERMINOLOGY

Entity --> What is this table about? students

Attribute (Field) --> What items of information are necessary to keep concerning this entity?ID, name, department, year, advisor

Record (Tuple) --> A set of values for each attribute for one item20027654 Ali Kaya CAA 2 Ahmet Durukal

N. Fenmen - CAA292 Database Applications for Business - 2003 - 2004 Spring

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DATABASE MANAGEMENT SYSTEMS

Key --> The attribute used to define a required itemwho is the advisor of Ali Kaya?

Types of keys:

* Primary Key: Key used to uniquely identify a record * Foreign Key: A field in this table which is the Primary key of another table

Relationship --> Definitions linking two or more tables

N. Fenmen - CAA292 Database Applications for Business - 2003 - 2004 Spring