slide môn học MySQL bài 1 database foundation knowledge

Database Foundation knowledge
Session 1


Objectives(1)


Explain why we need a database



Explain the evolution of database management
systems



Describe the basic concepts related to a
database

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Objectives(2)




Explain the basic
Relational database

concepts

•

Entity integrity

•

Primary key

•

Foreign key

•

Relation and its degree

related

to

a

Describe a brief introduction of SQL
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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?”
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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
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Need for permanency
Data storage can be achieved even
using simple manual files.

However, data stored in this form
is not permanent.

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Problems with file storage
The process of manually
maintaining data through files is :





Tedious
time consuming
Error prone.

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Evolution of DBMS-1
What is a DBMS?
Database
A003

Allen

A007

Shane

A004

Brian

A008

Ricky

Retrieve Data

Insert Data

Update Data

DBMS

Delete Data

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Basic Concepts of a
database-1
Data
Player

Matches
Won in
the Series

Information

Lleyton Hewitt

20

Best Player of
the Series

Carlos Moya

15

Lleyton Hewitt

Marat Safin

10

Paradorn
Srichaphan

8

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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

Columns

Rows

and columns
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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.

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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.

Unique key

RollNumber

Name

1

Sam

2

John

3

Jenny

3

Lisa

Wrong
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Basic Concepts of a Relational
database-1
Relational
Database

Applications for
interacting with
data in DB

RDBMS
A suite of S/W
programs to create,
maintain DB

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Basic Concepts of a Relational
database-2
Entities

Tables

Attributes
Fields
Relations

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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.

Primary Key

Roll
Number

Student Name

1

Sam

2

John

3

Jenny

4

Lisa

5

Penny

6

Peter

7

Joe
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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
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Foreign key
Two tables are linked together using a foreign key.
P
F

Roll Number

Student Name

1

Sam

2

John

3

Jenny

2

John

65

4

Lisa

4

Lisa

90

5

Penny

6

Peter

87

6

Peter

7

Joe

89

7

Joe

Roll
Number

Student
Name

Marks
Obtained

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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.
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Relation and degree
According to the relational model, every relation or
table is made up of many tuples. They are also
called records.
For eg:

CHN

China

Renminbi (Yuan)

FRN

France

Francs

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