Chapter 2 part 1(Database System)

By the end of this lesson, student will be able to:

2.1 Define database

2.2 Describe components of a database table

2.3 Describe the characteristics of relation scheme

2.4 Identify relation keys

2.5 Explain integrity rules

2.6 Explain relational model relationships

Database• A collection of related data• Shared collection of logically related data (and a description

of this data), designed to meet the information needs of an organization.

Data Known facts that can be recorded and have an implicit

meaning/ Raw facts; that is, facts that have not been yet processed to reveal their meaning to the end user.

Information Facts (data) that are arranged in meaningful patterns

Relational database is a collection of tables

Heading: table name and column names

Body: rows, occurrences of data

StdSSN StdLastName StdMajor StdClass StdGPA 123-45-6789 WELLS IS FR 3.00 124-56-7890 NORBERT FIN JR 2.70 234-56-7890 KENDALL ACCT JR 3.50

Student

• Typically include: 1) Numeric data types for integers and real numbers2) Characters3) Booleans4) Fixed-length strings5) Variable-length strings6) Date, time, timestamp7) Money / Currency8) Other special data types

Marina G. Erechtchoukova 8

Schema:Book (Bid: char(2), Title: char(50),

Author:char(20), Price: decimal(5,2)) Instance: Bid Title Author Price

11 Franklin forgets Bourgeois 7.00

22 Arthur and the Seventh-Inning Stretcher Krensky 14.00

33 Midnight Wrestlers Morgan 11.00

44 Midnight Pilot Morgan 9.00

55 Book of Science Activities 18.00

Yards

Yard Number

Owner

Address

Phone Number

1 2

3

4

1) What is the name of the relation?2) What is the cardinality of the relation?3) What is the degree of the relation?4) What is the domain of StdGPA? What is the

domain of StdSSN?

StdSSN StdLastName StdMajor StdClass StdGPA 123-45-6789 WELLS IS FR 3.00 124-56-7890 NORBERT FIN JR 2.70 234-56-7890 KENDALL ACCT JR 3.50

Student

Answer the question below based on the following tables:

LECTURER

Identify attribute, domain, tuple, and cardinality

StaffNum ICNum Name Posit ion Department PhoneNumIT001 781103-03-5333 Abdullah Pensyarah Kejuruteraan perisian 09-8840023

IT002 680923-11-4908 Maimunah Prof Madya Sains komputer 09-8840024IT003 801204-06-2323 Kamal Pensyarah Sistem maklumat 09-8840025IT004 600720-06-5380 Jamilah Prof Madya Multimedia 09-8840026IT005 590101-01-2425 Hakim Professor Kejuruteraan perisian 09-8840027IT006 810303-19-9923 Anis Pensyarah Multimedia 09-8840028

LECTURER

GRADE STUDENT

1) Identify attribute, domain, tuple, degree and cardinality for table GRADE & STUDENT.

2) Transform each table to relation schema.

StudentNum CourseCod

e

Grade

P1050 SK001 2.50

L2115 SM100 3.00

L4213 KP222 3.00

P2020 SM100 3.50

StudentNum Name CourseCode

P1050 Azura SK001

L2115 Chong SM100

L4213 Karim KP222

P2020 Ahmad SM100

1) Candidate key- Any set of one or more columns whose combined values are

unique among all occurrences (i.e., tuples or rows). - Since a null value is not guaranteed to be unique, no

component of a candidate key is allowed to be null. - There can be any number of candidate keys in a table .

2) Primary key- Any candidate key of that table which the database designer

arbitrarily designates as "primary".- The primary key may be selected for convenience,

comprehension, performance, or any other reasons.

3) Foreign key- A set of one or more columns in any table which may hold

the value(s) found in the primary key column(s) of some other table.

1) What is the candidate key ?2) What is the primary key?3) Transform the table to relation schema.

Identify the relational key available in each relation.

Data integrity means that the data values in the database are correct and consistent.

Integrity constraints provide a way of ensuring that changes made to the database by authorized users do not result in a loss of data consistency

Data integrity is enforced in the relational model by:

1) Entity integrity

2) Referential integrity

Entity Integrity- The entity integrity rule states that for every instance of an

entity, the value of the primary key must exist, be unique, and cannot be null.

- Without entity integrity, the primary key could not fulfill its role of uniquely identifying each instance of an entity.

Referential Integrity- The referential integrity rule states that every foreign key

value must match a primary key value in an associated table.

- Referential integrity ensures that we can correctly navigate between related entities.

1) One to many2) Many to many3) Self referencing

• One Birdfeeder is visited by Many Birds• One Yard contains Many Birdfeeders• One Patient has Many Prescriptions• One Insurance has Many Patients• One Student attends Many Classes

• One to Many relationships are the most common relationships.

• A record MUST be in the One table in order to appear in the Many table.

• One to Many includes One to None.

1 ∞Medical Record #

Patients Prescription Number

Medical Record #

Medications

Primary Key linked to Non Primary Key

Example 1:

Bird Feeders

Bird Feeder Number

Material

Location in Yard

Yard Number

Yards

Yard Number

Owner

Address

Phone Number

Each Birdfeeder can only be in one Yard, but each Yard can have many Birdfeeders. This is called a one to many (1 - ∞) Relationship.

• Many Students are taught by Many Teachers• Many Patients see Many Doctors• Many Medications are taken by Many Patients• Many Customers buy Many Products

Many to Many relationships are also very common.

∞ ∞Shands Medical Record #

Medicare Patients Prescription Number

Shands Medical Record #

Medications

Non Primary Key linked to Non Primary Key

Example:

Access sees this as an Indeterminate relationship

You cannot Enforce Referential Integrity

Indeterminate relationships are often found when we are linking tables, because Linked Tables cannot have a primary key.

If you have imported or created a table, it’s very rare to have a need for an indeterminate Relationship.

These relationships show Access that the data saved in the field from the first table is the same kind of data saved in the second table, but there can be no data integrity rules applied on indeterminate relationships.

ExamplesPatients

Patient ID

First

Last

Address

City

State

Zip

Medications

Med ID

Medication

Description

Patient Meds

PM ID

Patient ID

Med ID

Dosage

Directions

1

One Patient can take many

Medications∞

1

One Kind of Medication can be

taken by Many Patients

∞

ExamplesPatients

Patient ID

First

Last

Address

City

State

Zip

Primary Drs

Doc ID

Name

Phone

Pager

email

ExamplesPatients

Patient ID

First

Last

Address

City

State

Zip

Primary Drs

Doc ID

Name

Phone

Pager

email

One Patient will have only ONE primary Doctor.One Primary Doctor can have MANY patients.

Primary Doc

1

∞

ExamplesPatients

Patient ID

First

Last

Address

City

State

Zip

Med History

Patient ID

Health Q1

Health Q2

Health Q3

Health Q4

ExamplesPatients

Patient ID

First

Last

Address

City

State

Zip

Med History

Patient ID

Health Q1

Health Q2

Health Q3

Health Q4

One Patient will have only ONE Medical History.Each Medical History will belong to only ONE patient.

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