Database Design – Lecture 17

Database Design – Lecture 17

Database Design Strategies: Top Down/Bottom UP

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Lecture Objectives Top Down Database Design Bottom Up Database Design

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Top Down Database Design Done from a business overview -

narrative Conceptual Database Design

Relational: Entity Relationship Diagram Object Oriented: Object Oriented Data

Model Components:

Entities Attributes Relationship

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Top Down Database Design Top Down Design Steps

1. Define possible entities and relationships2. Define assumptions about relationships3. Create initial ERD or OODM, including

relationships and multiplicity4. Define the possible attributes for each entity5. If OODM, convert to a class diagram and then

convert class diagram to relational6. Normalize and create the relational schema

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Top Down Database Design Conceptual Model Examples

Entity Relationship Diagram (with attributes and relationships)

CUSTOMER

PK CUST_NUM

CUST_LNAME CUST_FNAME CUST_INITIAL CUST_EMAIL

VIDEO

PK VIDEO_ID

VIDEO_CLASS VIDEO_TITLE VIDEO_CHG

RENTAL

PK RENTAL_IDPK,FK1 CUST_NUM

RENTAL_OUT RENTAL_RETURNFK2 VIDEO_ID

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Top Down Database Design ERD - Relational Schema

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Top Down Database Design Conceptual Model Examples:

Object Oriented Data Model

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Top Down Database Design Class Diagram

Plan

planIDtitle

Client

clientIDaccounttitleaddrestelephonefax

1..n1

has

1..n1

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Top Down Database Design Tables:

PLAN (PLAN_ID (pk), TITLE) CLIENT (CLIENT_ID (pk), ACCOUNT, TITLE,

ADDRESS, TELEPHONE, FAX, PLAN_ID (fk))

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Bottom UP Database Design - Relational

Done from examples of reports or screens or just data

Take data samples and convert them to entities with attributes and relationships

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Bottom Up Design Steps1. Collect list of attributes2. Define functional dependencies3. Define unique identifier(s)4. Make sure you have 1NF5. Define partial dependencies6. Normalize to 2NF7. Define transitive dependencies8. Normalize to 3NF

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Bottom Up Design Steps9. Define relationships and connectivity

types10. Create ERD11. Make sure attributes are atomic and other

relational database modeling techniques (I.e. description – long text)

12. Review ERD and complete relational database model

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Bottom Up Design Steps – Data only example

Given these attributes:EMP_CODE 1003LAST_NAME WillakerEDUCATION HS, BBA, MBADEPT_CODE MKTGDEPARTMENT MarketingDEPT_MANAGER Jill H. MartinJOB_CLASS 23TITLE Sales AgentDEPENDENTS Gerald (spouse), Mary (daughter),

John (son)BIRTH_DATE 12/23/65HIRE_DATE 10/14/94TRAINING Level 1, Level 2BASE_SALARY $32, 255

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Given these attributes, we created tables:

EMPLOYEE (EMP_CODE (pk), LAST_NAME, BIRTH_DATE, HIRE_DATE, DEPT_CODE (fk), JOB_CLASS (fk))

DEPARTMENT (DEPT_CODE (pk), DEPARTMENT, DEPT_MANAGER)

JOB (JOB_CLASS (pk), TITLE, BASE_SALARY)

DEPENDENT_TYPE (DEP_TYPE (pk), ROLE)

DEPENDENT (DEP_CODE (pk), EMP_CODE (pk, fk), FIRST_NAME, DEP_TYPE (fk))

TRAINING (TRAIN_ID (pk), TRAINING_NAME)

EMP_TRAINING (EMP_CODE (pk, fk), TRAIN_ID (pk, fk), DATE)

EDUCATION (EDUC_CODE (pk), EDUC_NAME)

EMP_EDUCATION (EMP_CODE (pk, fk), EDUC_CODE (pk, fk))

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Bottom UP Database Design – New Approach

Main Form/Sub Form approach1. Consider main form/sub form as the entities

in 1NF2. List the attributes for each entity and

normalize3. Make sure attributes are atomic and other

relational database modeling techniques (I.e. multi-valued dependencies)

4. Consider relationships and connectivity types5. Create complete relational database model

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Main Form/Sub Form Approach Example Form:Rogers Cable InvoiceInvoice Date: Sep. 24, 2001

Customer NameAccount: 230-16-161Due date: October 17, 2001New ChargesInformation ServicesRogers@Home Service 39.95Rogers@Home Outlet 10.00Rogers@Home Cable Modem Rental 0.00Tax

GST#89223 3.50Total New Charges 53.45

Main Form

Sub Form

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Main Form/Sub Form Approach

1. Consider main form/sub form as the entities in 1NF

Main form:INVOICE (INVOICE_NUM, DATE, ACCOUNT_NUM,

CUSTOMER_NAME, DUE_DATE)*Do not include tax and total, both of which are derived.*Assign a unique identifier

Sub form: INVOICE_CHARGES (SERVICE_NAME, CHARGE)

*Need to recognize that this is for a specific invoice AND there could be multiple (therefore duplicate) services on an invoice.

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2. List the attributes for each entity and normalize

INVOICE_NUM

DATE

ACCOUNT_NUM

CUSTOMER_NAME

DUE_DATE

1NF 2NF 3NF

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1NF:INVOICE (INVOICE_NUM (pk), DATE, ACCOUNT_NUM, CUSTOMER_NAME, DUE_DATE)

2NF (NONE)

3NF INVOICE (INVOICE_NUM (pk), DATE, ACCOUNT_NUM (fk), DUE_DATE)

CUSTOMER (ACCOUNT_NUM (pk), CUSTOMER_NAME)

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INVOICE_NUM

LINE_NUM

SERVICE_NAME

CHARGE

1NF 2NF 3NF

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1NF:INVOICE_CHARGES (INVOICE_NUM (pk), LINE_NUM (pk), SERVICE_NAME, CHARGE)

2NF (NONE)

3NF (NONE)INVOICE_CHARGES (INVOICE_NUM (pk), LINE_NUM (pk), SERVICE_NAME (fk))

SERVICE (SERVICE_NAME (pk), CHARGE)

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3. Make sure attributes are atomic and other relational database modeling techniques INVOICE (INVOICE_NUM (pk), DATE, ACCOUNT_NUM (fk), DUE_DATE)

CUSTOMER (ACCOUNT_NUM (pk), CUST_FNAME, CUST_LNAME)

INVOICE_CHARGES (INVOICE_NUM (pk), LINE_NUM (pk), SERVICE_ID (fk))

SERVICE (SERVICE_ID (pk), SERVICE_NAME, CHARGE)

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4. Consider relationships and connectivity types (already taken into account)

INVOICE (INVOICE_NUM (pk), DATE, ACCOUNT_NUM (fk), DUE_DATE)

CUSTOMER (ACCOUNT_NUM (pk), CUST_FNAME, CUST_LNAME)

INVOICE_CHARGES (INVOICE_NUM (pk, fk), LINE_NUM (pk), SERVICE_ID (fk))

SERVICE (SERVICE_ID (pk), SERVICE_NAME, CHARGE)

*Note, what is not obvious here is the relationship between CUSTOMER and SERVICE and the fact that a customer can have more than one service and vice versa.

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6. Create complete relational database model

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Main Form/Sub Form approach The hotel Blue Moon has a number of

branches across the country. All of them are in need of furniture. The hotel has a few suppliers who specialize in some particular kind of furniture. The Head Office wants to keep track of all purchases using the following type of reports.

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Supplier: Fine Furniture Customer: Blue Moon at Morin CityAddress: 15 Main Street Address: 1 Front StreetMorin City, Y6F 7R9 Morin City, Y6F 4P8Contact: Steve Good Tel: 444-888-777Tel: 444-555-6666

Line # Invoice # Invoice Date

Furniture ID – Title

Number Of Items

Item Price Total Paid Paid by chq #

1 111 01/29/11 B11 – Bed 10 200 2000 123-123-444

2 C11 – Chair

25 100 2500

3 D11 – Desk

2 350 700

4 Total for Invoice

$5200.00

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6 122 02/26/01 C11 – Chair

5 100 500 123-123-545

7 B12 – King Bed

10 600 6000

8 Total for Invoice

$6500.00

Sample Purchasing Report:

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Supplier: Fine Furniture Customer: Blue Moon at Morin CityAddress: 15 Main Street Address: 1 Front StreetMorin City, Y6F 7R9 Morin City, Y6F 4P8Contact: Steve Good Tel: 444-888-777Tel: 444-555-6666

Line # Invoice # Invoice Date

Furniture ID – Title

Number Of Items

Item Price Total Paid Paid by chq #

1 111 01/29/11 B11 – Bed 10 200 2000 123-123-444

2 C11 – Chair

25 100 2500

3 D11 – Desk

2 350 700

4 Total for Invoice

$5200.00

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6 122 02/26/01 C11 – Chair

5 100 500 123-123-545

7 B12 – King Bed

10 600 6000

8 Total for Invoice

$6500.00

Sample Purchasing Report:

Main Form Sub Form(excluding totals)

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Main Form/Sub Form Approach Step 1: Consider main form/sub form as the entities in 1NF

Main FormAssume there are two distinct tables in the main form SUPPLIER, CUSTOMER

SUPPLIER (SUPPLIER_NAME, SUPPLIER_ADDRESS, SUPPLIER_CONTACT, SUPPLIER_TEL)

CUSTOMER (CUSTOMER_NAME, CUSTOMER_ADDRESS, CUSTOMER_TEL)

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Sub Form:Get rid of repeating groups

Rows 2, 3 and 7 contain empty cells. They assume the values of the rows above themRows 4 and 8 contain values for another business entity – total for invoice; a derived value. Ignore these rows.

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Sub Form:Get rid of repeating groups

PAYMENT (INV_NUM, INV_DATE, FURN_ID_TITLE, QTY, ITEM_PRICE, TOTAL, CHEQUE_NUM)

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Main Form/Sub Form Approach Step 2: List the attributes for each entity

and normalize Step 3: Make sure attributes are atomic

and other relational database modeling techniques (I.e. multi-valued dependencies)

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Main Form/Sub Form ApproachSUPPLIER (SUPPLIER_NAME, SUPPLIER_ADDRESS,

SUPPLIER_CONTACT, SUPPLIER_TEL) Need to create a unique identifier Need to make attributes atomic (SUPPLIER_ADDRESS

and SUPPLIER_CONTACT)

SUPPLIER (SUPPLIER_ID (pk), SUPPLIER_NAME, SUPPLIER_STREET_NUMBER, SUPPLIER_STREET, SUPPLIER_CITY, SUPPLIER_PROVINCE, SUPPLIER_POSTAL_CODE, SUPPLIER_CONTACT_LNAME, SUPPLIER_CONTACT_FNAME, SUPPLIER_TEL)

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Main Form/Sub Form ApproachCUSTOMER (CUSTOMER_NAME, CUSTOMER_ADDRESS,

CUSTOMER_TEL) Need to create a unique identifier Need to make attributes atomic

(CUSTOMER_ADDRESS)

CUSTOMER (CUSTOMER_ID (pk), CUSTOMER_NAME, CUSTOMER_STREET_NUMBER, CUSTOMER_STREET, CUSTOMER_CITY, CUSTOMER_PROVINCE, CUSTOMER_POSTAL_CODE, CUSTOMER_TEL)

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Main Form/Sub Form ApproachPAYMENT (INV_NUM, INV_DATE, FURN_ID_TITLE, QTY,

ITEM_PRICE, TOTAL, CHEQUE_NUM Need to make attributes atomic (FURN_ID_TITLE

FURN_ID, FURN_NAME) TOTAL is a derived attribute – ignore it Need to create a unique identifier

PAYMENT (INV_NUM (pk), INV_DATE, FURN_ID (pk), FURN_NAME, QTY, ITEM_PRICE, CHEQUE_NUM)

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Main Form/Sub Form Approach Step 2: Normalize PAYMENT

INVOICE(INV_NUM (pk), INV_DATE, CHEQUE_NUM)

FURNITURE (FURN_ID (pk), FURN_NAME, ITEM_PRICE)

INV_DETAIL (INV_NUM (pk, fk), FURN_ID (pk, fk), QTY, ITEM_PRICE)

INV_NUM

INV_DATE

FURN_ID

FURN_NAME

QTY

ITEM_PRICE

CHEQUE_NUM

1NF 2NF

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Main Form/Sub Form Approach Step 4: Consider relationships and

connectivity types Relationships:

CUSTOMER:INVOICE – 1:MSUPPLIER:INVOICE – 1:MINVOICE:INVOICE_DETAIL – 1:M

INVOICE – INVOICE_DETAIL is strong/weak entity

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Main Form/Sub Form Approach Step 5: Create complete relational

database model

SUPPLIER (SUPPLIER_ID (pk), SUPPLIER_NAME, SUPPLIER_STREET_NUMBER, SUPPLIER_STREET, SUPPLIER_CITY, SUPPLIER_PROVINCE, SUPPLIER_POSTAL_CODE, SUPPLIER_CONTACT_LNAME, SUPPLIER_CONTACT_FNAME, SUPPLIER_TEL)

CUSTOMER (CUSTOMER_ID (pk), CUSTOMER_NAME, CUSTOMER_STREET_NUMBER, CUSTOMER_STREET, CUSTOMER_CITY, CUSTOMER_PROVINCE, CUSTOMER_POSTAL_CODE, CUSTOMER_TEL)

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Main Form/Sub Form Approach Step 5: Create complete relational

database model (cont’d)

INVOICE(INV_NUM (pk), INV_DATE, CHEQUE_NUM, SUPPLIER_ID (fk), CUSTOMER_ID (fk))

FURNITURE (FURN_ID (pk), FURN_NAME, ITEM_PRICE)

INV_DETAIL (INV_NUM (pk, fk), LINE_NUM (pk), FURN_ID (fk), QTY, ITEM_PRICE)

• LINE_NUM (pk) added to ensure integrity of sequence of date

• INV_NUM made pk and fk (existence dependence)

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Database Design – Lecture 17