slide môn học MySQL bài 1 database foundation knowledge

What is a database?A database is an organized form of data consisting of one or more related data items called records.. A database is like a data collection to which we can ask differe

Database Foundation

knowledge Session 1

 Explain why we need a database

 Explain the evolution of database management

systems

 Describe the basic concepts related to a

database

 Explain the basic concepts related to a Relational database

• Entity integrity

• Primary key

• Foreign key

• Relation and its degree

 Describe a brief introduction of SQL

What is a database?

A database is an organized form of data consisting

of one or more related data items called records

A database is like a data collection to which we can ask different questions

For example, “What are the phone numbers and addresses of the five nearest post offices?”

Why use databases?

Databases are used to store data in an efficient and organized manner A database allows us quick and easy management of data

For example, a company may maintain details of its employees in a database

FirstName LastName Hiredate

Karla Jablonski 1994-03-11 Martine Rance 1992-02-05 Margaret Smith 1988-09-29 Gary Thomas 1988-08-09

Need for permanency

Data storage can be achieved even

using simple manual files

However, data stored in this form

is not permanent

Problems with file storage

The process of manually

maintaining data through files is :

 Tedious

 time consuming

 Error prone.

Evolution of DBMS-1

Retrieve Data

Insert Data

Update Data Delete Data

Brian A004

Allen

A003

Ricky A008

Shane A007

Database

What is a DBMS?

Basic Concepts of a

database-1

Data

Player Matches Won in

the Series

Lleyton Hewitt 20

Carlos Moya 15

Marat Safin 10

Paradorn

Srichaphan 8

Information

Best Player of the Series

Lleyton Hewitt

Basic Concepts of a

database-2

Tables are database

objects that contain

all the data present

in a database

Data in a table is

arranged in rows

and columns

Columns

Row s

Basic Concepts of a

database-3

 A database system is a computer-based record keeping system whose overall purpose is to record and maintain information

 A DBMS is a collection of related records and a set of programs that access and manipulates these records

Basic Concepts of a

database-4

 Duplication of data or

‘data redundancy’ can be

reduced using a database

management system

 Ensuring the accuracy of

data in the database is

called maintaining the

integrity of data

RollNumber Name

Unique key

Basic Concepts of a Relational

database-1

Applications for

interacting with

data in DB

Relational Database

RDBMS

A suite of S/W programs to create,

maintain DB

Basic Concepts of a Relational

database-2

Entities

Attributes

Relations

Tables

Fields

Basic concepts of Relational

Database-3

A database is a collection

of tables Each table

contains information about

a single entity

A primary key is a column

or combination of columns

that uniquely identifies a

record

Roll Number Student Name

1 Sam

2 John

3 Jenny

4 Lisa

5 Penny

6 Peter

7 Joe

Primary Key

Entity Integrity

 The Entity integrity rule

states that no component

of the primary key of a

base table should be

allowed to accept NULL

values

 A NULL value is a missing

value

Roll Number Student Name

1 Sam

2 John

3 Jenny

4 Lisa

5 Penny

Peter

7 Joe

Invalid

Foreign key

Two tables are linked together using a foreign key

Roll Number Student Name

1 Sam

2 John

3 Jenny

4 Lisa

5 Penny

6 Peter

7 Joe

Roll Number Student Name Marks Obtained

2 John 65

4 Lisa 90

6 Peter 87

7 Joe 89

P

F

Referential Integrity

The Referential integrity rule states that a

database must not contain any unmatched foreign key values

The DBMS is responsible for ensuring that the

attribute values in the foreign key are valid and

have a corresponding match in the relation where

the attribute is a primary key

Relation and degree

The number of attributes within a table is called the degree of that table

CHN China Renminbi (Yuan) FRN France Francs

According to the relational model, every relation or table is made up of many tuples They are also

called records

For eg: