Database Design and Administration By: Sahar Mosleh

Sahar Mosleh California State University San Marcos

Database Design and Administration

By:Sahar Mosleh


Relational Data Model


File Management Systems

• Before the existence of DBMS, the data were stored in separate files.

• There was no link from one file to another

• If the structure of the data changed (ex: adding more fields), programs that were using the file had to change

• Problems became more severe when the number of the programs using the files increased over time


Relational Data Model

Definition:• A relational database is a database where all data visible to

users is organized strictly as tables of data values and where all database operations work on these tables

• In this model information is stored in a database as simple row/column tables of data

• Next slide shows an example of tables in a relational database


Empl_Num Name Age Rep_Office Title Hire_Date Manager Quota Sales105 Bill Adams 37 13 Sales Rep 12-FEB-88 104 350000 367911109 Mary Jones 31 11 Sales Rep 12-OCT-89 106 300000 392725102 Sue Smith 48 21 Sales Rep 10-DEC-86 108 350000 474050106 Sam Clark 52 11 VP Sales 14-JUN-88 275000 299912104 Bob Smith 33 12 Sales Mgr 19-MAY-87 106 200000 142594101 Dan Roberts 45 12 Sales Rep 20-OCT-86 104 300000 305673110 Tom Synder 41 Sales Rep 13-JAN-90 101 75985108 Larry Fitch 62 21 Sales Mgr 12-OCT-89 106 350000 361865103 Paul Cruz 29 12 Sales Rep 01-MAR-87 104 275000 286775

1 Nacy Angelli 49 22 Sales Rep 14-NOV-88 108 300000 186042 ….….

SalesReps

Order_Num Order_Date Cust Rep MFR Product QTY Amount 112961 17-DEC-89 2117 106 REI 2A44L 7 31500 113012 11-JAN-90 2111 105 ACI 41003 35 3745 112989 03-JAN-90 2101 106 FEA 114 6 1458 113051 10-FEB-90 2118 108 QSA K47 4 1420 112968 12-OCT-89 2102 101 ACI 41004 34 3978 113036 30-JAN-90 2107 110 ACI 4100Z 9 22500 113045 02-FEB-90 2112 108 REI 2A44R 10 45000 112963 17-DEC-89 2103 105 ACI 41004 28 3276 113013 14-JAN-90 2118 108 BIC 41003 1 652 113058 23-FEB-90 2108 109 FEA 112 10 1480 112997 08-JAN-90 2124 107 BIC 41003 1 652 112983 27-DEC-89 2103 105 ACI 41004 6 702 113024 20-JAN-90 2114 108 QSA XK47 20 7100 113062 24-FEB-90 2124 107 FEA 114 10 2430 112979 12-OCT-89 2114 102 ACI 4100Z 6 15000 ……

Orders

Mfr_Id Product_Id Description Price Qty_On_HandREI 2A45C RATCHET LINK 79 210ACI 4100Y WIDGET REMOVER 2750 25QSA XK47 REDUCER 355 38BIC 41672 PLATE 180 0IMM 779C 900-LB BRACE 1875 9ACI 41003 SIZE 3 WIDGET 107 207ACI 41004 SIZE 4 WIDGET 117 139BIC 41003 HANDLE 652 3IMM 887P BRACE PIN 250 24QSA XK48 REDUCER 134 203REI 2A44L LEFT HINGE 4500 12….

Products

Cust_Num Company Cust_Rep Credit_Limit 2111 JCP Inc. 103 50000 2102 First Corp. 101 65000 2103 Acme Mfg. 105 50000 2123 Carter and Sons 102 40000 2107 Ace International 110 35000 2115 Smithson Corp. 101 20000 2101 Jones Mfg. 106 65000 2112 Zetacorp 108 50000 2121 QMA Assoc. 103 45000 2114 Orion Corp. 102 20000 ……

Customers

Offices

Office City Region Mgr Target Sales 22 Denver Western 108 300000 186042 11 New York Eastern 106 575000 692637 12 Chicago Eastern 104 800000 735042 13 Atlanta Eastern 105 350000 367911 21 Los Angeles Western 108 725000 835915


Table

Definition:• A table is a rectangular object with rows and columns

• For example in the office table:• Each row of the office table represents a single physical entity• Each column of the offices table represents one item of data

that is stored in the database for each office:• Ex: City column represents the location of the office

• An alternative term for column is attribute

• Each row of the table contains exactly one data value in each column


• In each column of a table, all of the data values in that column have the same type. For example:

• City column values are words• Sales values are money type• Mgr values are integer

• Each column in a table has a column name which is written as a heading at the top of the column

• Column names must be unique in a table

• The columns of a table have a left-right order. That is defined when the table is first created.

• The order of the column has no effect when any action is done against the table


• Each table must have at least one column

• Almost all commercial DBMS products impose maximum of 255 columns per table

• A table can have zero or more rows

• A table with zero rows is called an empty table

• Order of the rows is not important in a table.

• Most relational DBMSs either do not impose any limit on the number of rows or their limit is a very large number

• A common limit is approximately 2 billion rows


Primary Key

Definition:• A primary key is a column or combination of two or more

columns that uniquely identifies each row of a table.

• Since the order of rows in a table is irrelevant, rows cannot be identified based on their positions in a table

• Ex: row 1, row 2, row 20

• In a well-designed relational database each table has a primary key.

• If the primary key contains two or more columns, it is called a composite primary key


Example of primary key

• Consider the Offices table

• “Office” column (attribute) can be a good choice for the primary key because each office has a different office id

• However, city is not a good choice because more than one office may be located in the same city.

Office City Region Mgr Target Sales 22 Denver Western 108 300000 186042 11 New York Eastern 106 575000 692637 12 Chicago Eastern 104 800000 735042 13 Atlanta Eastern 105 350000 367911 21 Los Angeles Western 108 725000 835915


• Consider the Products table

Mfr_Id Product_Id Description Price Qty_On_HandREI 2A45C RATCHET LINK 79 210ACI 4100Y WIDGET REMOVER 27.50 25QSA XK47 REDUCER 355 38BIC 41672 PLATE 180 0IMM 779C 900-LB BRACE 1875 9ACI 41003 SIZE 3 WIDGET 107 207ACI 41004 SIZE 4 WIDGET 117 139BIC 41003 HANDLE 652 3IMM 887P BRACE PIN 250 24QSA XK48 REDUCER 134 203REI 2A44L LEFT HINGE 4500 12….

• What is a good primary key for this table?


• In this case, MrfId by itself, is not a good choice to be a primary key because more than one manufacturer may produce more than one product

• Further, ProductId by itself is not a good choice either because the same product can be produced by more than one manufacturer.

• However, combination of both is unique in every row.

• This is an example of composite primary key.

• A table with a primary key is called a relation. A relation is a table in which no duplicate rows can exist.


Relationship

• How does the parent/child model is represented in the relational data model?

• Consider the following two tables

Empl_Num Name Age Rep_Office Title Hire_Date Manager Quota Sales105 Bill Adams 37 13 Sales Rep 12-FEB-88 104 350000 367911109 Mary Jones 31 11 Sales Rep 12-OCT-89 106 300000 392725102 Sue Smith 48 21 Sales Rep 10-DEC-86 108 350000 474050106 Sam Clark 52 11 VP Sales 14-JUN-88 275000 299912….….

SalesReps

Offices

Office City Regin Mgr Target Sales 22 Denver Western 108 300000 186042 11 New York Eastern 106 575000 692637 12 Chicago Eastern 104 800000 735042 13 Atlanta Eastern 105 350000 367911 21 Los Angeles Western 108 725000 835915


• The parent is the offices table

• The child is the salesreps table because the salesreps works in an office

• Relationships are created by having the same data in two or more tables

Empl_Num Name Age Rep_Office Title Hire_Date Manager Quota Sales105 Bill Adams 37 13 Sales Rep 12-FEB-88 104 350000 367911109 Mary Jones 31 11 Sales Rep 12-OCT-89 106 300000 392725102 Sue Smith 48 21 Sales Rep 10-DEC-86 108 350000 474050106 Sam Clark 52 11 VP Sales 14-JUN-88 275000 299912….….

SalesReps

Offices



• Note that the RepOffice column in salesreps table contains the office number of the sales office where each sales person works

• The values of the RepOffice column is the set of office numbers found in the office column of the offices table

• We will see how this restriction is imposed when we discuss about creating tables later in the course

• For example, it is possible to find the sales office where “Mary Jones” is working by finding the value of Mary Jones RepOffice (11) and finding the corresponding row offices table

• So, the parent/child relationship between two tables A and B is not represented by explicit pointers but by common data values stored in the two tables

• Programmers must specify this relationship when they create the tables


Foreign KeyDefinition:

• Foreign key is a column (or combination or two or more columns) whose value matches the primary key of another table or possibly the same table

• Together, primary key and the foreign key make the parent/child relationship in relational data models

Emp_Num Name Age Rep_Office Title Hire_Date Manager Quota Sales105 Bill Adams 37 13 Sales Rep 12-FEB-88 104 350000 367911109 Mary Jones 31 11 Sales Rep 12-OCT-89 106 300000 392725102 Sue Smith 48 21 Sales Rep 10-DEC-86 108 350000 474050106 Sam Clark 52 11 VP Sales 14-JUN-88 275000 299912….….

SalesReps

Offices


Primary key

Foreign key


Example of Foreign Key

Empl_Num Name 105 Bill Adams109 Mary Jones102 Sue Smith106 Sam Clark….

SalesReps

Order_Num Order_Date Cust Rep Mfr Product QTY Amount 11296 17-DEC-89 2117 106 REI 2A44L 7 31500 113012 11-JAN-90 2111 105 ACI 41003 35 3745 112989 03-JAN-90 2101 106 FEA 114 6 1458 113051 10-FEB-90 2118 108 QSA K47 4 1420 ….

Orders

Mfr_Id Product_IdREI 2A45C …..ACI 4100Y …..QSA XK47 ……….…..

Products Cust_Num 2111 ….. 2102 …. 2103 …. ………. …….

Customers


Entity Relational Diagram (ERD)

Modeling


ERD Model

• Entity-Relationship, ER Model• ER model describes data as entities, relationships and

attributes

• Entity• A “thing” in the real world with an independent existence• Physical existence

• Person, car, house or employee• Conceptual existence

• Company, job, university course

• Attribute• Property that describes entity• employee Name, Address, Age, HomePhone• companyName, Headquarters, President


• Value

• A particular entity will have a value for each of its attributes

• The attribute values that describe each entity become a major part of the stored data

• Example

• employee: Name, Address, Age, HomePhone

• e1: “Bill Adams”, “561 Machray Hall”, “25”, “8831”

• e2: “John Smith”, “563 Queen Hall”, “30”, “8833”


Simple and Derived Attributes

• Simple attribute• Attributes that are not divisible

• Ex: age, SSN, StudentId, etc

• Derived• Attributes that can be derived from other attributes either from

the same entity or other entities. For example:• Age can be derived from BirthDate or • GPA can be derived from Grades

• Attribute values can be derived from other entities. • NumberOfEmployees of a department in department entity

can be derived by counting the number of employees who work in that department in the employee entity


Null Values

• Not Applicable• A particular entity does not have an applicable value for an

attribute• ApartmentNumber is null because the family lives in the

house and not in an apartment• CollegeDegrees is null because the person never gone to

the college

• Unknown• Missing (value exists but not known)

• Height of a person• Not Known (existence is not sure)

• HomePhone, OfficePhone


Entity

• An entity defines a collection object that have the same attributes

• Entity is described by its name and attributes• Example:

• Employee [Number, Name, Title, Salary]• Project [Number, Budget, Location]

• Entity instances are instantiations of the entity• Example:

• Employee Joe, Jim, ...• Project Compiler design, Accounting, ...


ER Notation

• Entity • Rectangular box• Enclosing the entity name

• Attribute Name• Oval• Attached to its entity by straight line• Composite Attribute

• Attached to the component attribute by straight line

EMPLOYEE

EMPLOYEE

EmpId


Attribute Notations

Regular Attribute

KeyAttribute

DerivedAttribute


• Key Attribute• Values can be used to identify each entity uniquely. This

plays the role of primary key in a table• The key attribute is underlined in ER diagram

• Composite key Attribute s• Combination of the two or more attributes must be

distinct for each instance. This plays the role of composite primary key in a table

• Entities may have more than one attribute that can be chosen as key attribute. For example, StudentId and SSN. However, you only have to pick one as the key (primary key) for the entity

• Entities can only have one primary key


Entities

PROJECTSUPPLIER

PART EMPLOYEE

LOCATION DEPARTMENT

WAREHOUSE


Entities and Attributes

PROJECTSUPPLIER

PART

LOCATION DEPARTMENT

WAREHOUSE

SupplierNo

SupplierName

Location ProjectNo

ProjectName

Location

Wareh.No

Wareh.Name

Location PartNo

PartName

QTY WGT

City Dept.No

Dept.Name

Manager

EMPLOYEEEmp.No

Emp.Name

Title SalaryAddr


Entities, Attributes, and Relationship

PROJECTSUPPLIER

PART EMPLOYEE

LOCATION DEPARTMENT

WAREHOUSE

SupplierNo

SupplierName

LocationProjectNo

ProjectName

Budget

Wareh.No

Wareh.Name

Location PartNo

PartName

QTY WGT

City Dept.No

Dept.Name

Manager

are supplied by

supply

are used by

use

works on

has

Emp.No

Emp.Name

Title SalaryAddr

Containsis contained in


All NotationsRegular entity

Regular Key Derived

Or

Entities

Attributes

Relationships


Example of ERD

Employee No EmployeeName

SalaryTitle

Address

PROJECT

Budget

ProjectName

Project No

TotalEmp

Location

WORKS ON

Duration

Responsibility

WORKSON

EMPLOYEE


Relationships

• A relationship logically associates two or more entities with each other

• Binary relationship associates two entities

• Ternary relationship associates three entities with each other

• N-ary relationship associates n entities with each other


Relationship attributes

• Attributes can be attached to specific relationships.

• Attributes that belong to two different entities should be placed as the attribute of the relationship

• These values provide data about the relationship between the participating entity instances.

PROJECT

Budget

ProjectNameProject No

EMPLOYEE


SalaryTitle

Responsibility

WORKS ONWORKSON

Duration


Kinds of Relationships (Cardinality)

• Fundamental ones are:• One-to-one• Many-to-one (one-to-many)• Many-to-many

• NOTE: There can be multiple relationships between two entities

WORKS-IN

EMPLOYEEMANAGES

DEPARTMENT


One-to-One Relationship

• Each instance of an entity class E1 can be associated with at most one instance of another entity class E2 and vice versa.

• Example :• Each employee can work on at most one project and each

project employs at most one employee.

PROJECT

Budget


EMPLOYEE


SalaryTitle Responsibility

WORKS ONWORKSON

Duration

1 1


WorksOnRelationshipEMPLOYEE

PROJECT

e1

e2

e3

.

.

.

e4

p1

p2

p3

.

.

.

p4

One-to-One Relationship


One-to-Many relationship

• Each instance of one entity class E1 can be associated with zero or more instances of another entity class E2, but each instance of E2 can be associated with at most 1 instance of E1.

• Example :• Each employee can work on at most one project; each

project can employ many employees.

PROJECT

Budget


EMPLOYEE



WORKS ONWORKSON

Duration

N 1



PROJECT

e1

e2

e3

.

.

e4

p1

p2

p3

.

.

.

p4

e5

One-to-Many Relationship


Many-to-Many Relationship

• Each instance of one entity class can be associated with many instances of another entity class, and vice versa.

• Example :• Each employee can work on many projects; each project can

employ many employees

PROJECT

Budget


EMPLOYEE



WORKS ONWORKSON

Duration

N M



PROJECT

e1

e2

e3

.

.

e4

p1

p2

p3

.

.

.

p4

e5

Many-to-Many Relationship


MANAGES

1 1

EMPLOYEE PROJECT

ResponsibilityDuration

Budget

ProjectName

Project NoEmployee No EmployeeName

SalaryTitle

WORKS-ON

N M

Multiple Relationships


Mapping ERD to Table: Step 1:

• For each strong entity E in the ERD• Create a table T that includes all the simple attributes of E• Choose one of the key attributes of E as primary key for T• If the chosen key of E is composite, the set of simple attributes

that form it will together form the primary key of T

Example:

Project (ProjectNo, ProjectName, Budget) PROJECT

Budget

ProjectName

Project No

WORKS ON


Step 2: Binary one-to-one Relationship

• For each binary one-to-one relationship:

• As you did in step 1, create 2 tables T1 and T2 for entities E1 and E2 that relate to each other by one-to-one relationship.

• Choose one table (say T1) and include the primary key of T2 as a foreign key in T1.

• It is better to choose the table with total participation not the one with partial participation

• Include all the attributes of the relationship as attributes of T1

• In Summary: Create a foreign key and move relationship attributes to any side of the one-to-one relationship


PROJECT

Budget


EMPLOYEE



WORKS ONWORKSON

Duration

1 1

Table 1: EMPLOYEE (EmployeeNo, EmployeeName, Title, Salary, ProjectNo, Duration, Responsibility, )

Table 2: PROJECT (ProjectNo, ProjectName, Budget)

OR Table 1: PROJECT (ProjectNo, ProjectName, Budget, EmployeeNo,

Duration, Responsibility)Table 2: EMPLOYEE (EmployeeNo, EmployeeName, Title, Salary)

Foreign key that references Project table

Foreign key that references Employee table

Example of Binary one-to-one Relationship


PROJECT

Budget


EMPLOYEE


SalaryTitle

WORKS ONMANAGES

Start-Date

1 1

• In this case, because PROJECT has total participation and EMPLOYEE has partial participation, it is a better idea to do the following:

Table 1: PROJECT (ProjectNo, ProjectName, Budget, EmployeeNo, Start-Date)

Table 2: EMPLOYEE (EmployeeNo, EmployeeName, Title, Salary)

Another example of Binary one-to-one Relationship



Step 3: Binary One-to-Many Relationship

• For each regular binary one-to-many relationship do:

• As you did in step 1, create 2 tables T1 and T2 for entities E1 and E2 that relate to each other by one-to-Many relationship.

• Identify the table that represents the participating entity at the N-side (say this table is T1)

• Include the primary key of T2 as foreign key in T1

• Include any simple attributes of the one-to-many relationship as attributes of T1

• Summary: Create a foreign key and move relationship attributes to the N-side of the one-to-many relationship


PROJECT

Budget


EMPLOYEE



WORKS ONWORKSON

Duration

N 1

Table 1: EMPLOYEE (EmployeeNo, EmployeeName, Title, Salary, ProjectNo, Duration, Responsibility)

Table 2: PROJECT (ProjectNo, ProjectName, Budget)


Example of Binary One-to-Many Relationship


Step 4: Binary Many-to-Many Relationship

• For each binary many-to-many relationship

• As you did in step 1, create 2 tables T1 and T2 for entities E1 and E2 that relate to each other by many-to-many relationship.

• Create a new Table T3

• Include as foreign key attributes in T3 the primary keys of T1 and T2. Their combination will form the primary key of T3

• Include any simple attributes of the many-to-many relationship as attributes of T3

• Summary: Each many-to-many relationship becomes a table with foreign keys to the participants


PROJECT

Budget


EMPLOYEE



WORKS ONWORKSON

Duration

N M

Table 1: EMPLOYEE (EmployeeNo, EmployeeName, Title, Salary)Table 2: PROJECT (ProjectNo, ProjectName, Budget) Table 3: WORKS-ON (EmployeeNo, ProjectNo, Duration, Responsibility)


Example of Binary Many-to-Many Relationship



Some Comments

• When you create your ERD, it is a better idea to follow the following general rules

• You should use the convention that entity type and relationship type names are in uppercase letters, attribute names are capitalized and role names are in lowercase letters

• Another naming consideration involves choosing binary relationships names to make the ERD of the schema readable from left to right and from top to bottom


Example:• Given the following ERD find the corresponding tables.

Flight: FlightNo, DestinationPassenger: PassNo, PassName, PassAddrFly: FlightNo, PassNo, SeatNo, MealBaggage: BagNo, Weight, PassNo


Student

Department

Course Major

Faculty

take

gives

Belongs-to

teach offersCan-take

N 1

1

N

1

1

M

N

MN

N

M

St-id St-Name St-emailsemester Maj-id

Maj-Name

Fac-id Fac-NameDep-id Dep-Name

Dep-Location

•Part of the Lab 1 Question:Given the following ERD, find the corresponding tables.

Database Design and Administration By: Sahar Mosleh

Documents

Transcript of Database Design and Administration By: Sahar Mosleh