database design 4: deriving tables from data models cs 320

Database Design 4: Deriving Tables From Data Models

CS 320

Review: Relationships in TablesCUST_ID CUST_NAME CUST_TYPE CUST_ADDR CUST_ZIP CUST_PHONE USERNAME PASSWORD

1 Jones, Joe P 1234 Main St. 91212 434-1231 jonesj 12342 Armstrong,Inc. R 231 Globe Blvd. 91212 434-7664 armstrong 33333 Sw edish Burgers R 1889 20th N.E. 91213 434-9090 sw edburg 23534 Pickled Pickles R 194 CityView 91289 324-8909 pickpick 53335 The Candy Kid W 2121 Main St. 91212 563-4545 kidcandy 23516 Waterman, Al P 23 Yankee Blvd. 91234 w ateral 89007 Bobby Bon Bons R 12 Nichi Cres. 91212 434-9045 bobbybon 30118 Crow sh, Elias P 7 77th Ave. 91211 434-0007 crow el 10339 Montag, Susie P 981 Montview 91213 456-2091 montags 9633

10 Columberg Sw eets W 239 East Falls 91209 874-9092 columsw e 8399

PURCH_ID PROD_ID CUST_ID PURCH_DATE DELIVERY_DATE POUNDS STATUS1 1 5 28-Oct-04 28-Oct-04 3.5 PAID2 2 6 28-Oct-04 30-Oct-04 15 PAID3 1 9 28-Oct-04 28-Oct-04 2 PAID3 3 9 28-Oct-04 28-Oct-04 3.7 PAID4 3 2 28-Oct-04 3.7 PAID5 1 7 29-Oct-04 29-Oct-04 3.7 NOT PAID5 2 7 29-Oct-04 29-Oct-04 1.2 NOT PAID5 3 7 29-Oct-04 29-Oct-04 4.4 NOT PAID6 2 7 29-Oct-04 3 PAID7 2 10 29-Oct-04 14 NOT PAID7 5 10 29-Oct-04 4.8 NOT PAID8 1 4 29-Oct-04 29-Oct-04 1 PAID8 5 4 29-Oct-04 7.6 PAID9 5 4 29-Oct-04 29-Oct-04 3.5 NOT PAID

PROD_ID PROD_DESC PROD_COSTPROD_PRICE1 Celestial Cashew Crunch 7.45$ 10.00$ 2 Unbrittle Peanut Paradise 5.75$ 9.00$ 3 Mystery Melange 7.75$ 10.50$ 4 Millionaire’s Macadamia Mix 12.50$ 16.00$ 5 Nuts Not Nachos 6.25$ 9.50$

Created byshared key fields

Types of Database Key Fields

Primary keys Foreign keys Composite keys

Review: Primary Key Uniquely identify a record Must be unique with respect to all other records in the

table You can create surrogate keys to serve as primary keys


CUST_ID CUST_NAME CUST_TYPE CUST_ADDR CUST_ZIP CUST_PHONE USERNAME PASSWORD1 Jones, Joe P 1234 Main St. 91212 434-1231 jonesj 12342 Armstrong,Inc. R 231 Globe Blvd. 91212 434-7664 armstrong 33333 Sw edish Burgers R 1889 20th N.E. 91213 434-9090 sw edburg 23534 Pickled Pickles R 194 CityView 91289 324-8909 pickpick 53335 The Candy Kid W 2121 Main St. 91212 563-4545 kidcandy 23516 Waterman, Al P 23 Yankee Blvd. 91234 w ateral 89007 Bobby Bon Bons R 12 Nichi Cres. 91212 434-9045 bobbybon 30118 Crow sh, Elias P 7 77th Ave. 91211 434-0007 crow el 10339 Montag, Susie P 981 Montview 91213 456-2091 montags 9633


CUST_ID CUST_NAME CUST_TYPE CUST_ADDR CUST_ZIP CUST_PHONE USERNAME PASSWORD1 Jones, Joe P 1234 Main St. 91212 434-1231 jonesj 12342 Armstrong,Inc. R 231 Globe Blvd. 91212 434-7664 armstrong 33333 Sw edish Burgers R 1889 20th N.E. 91213 434-9090 sw edburg 23534 Pickled Pickles R 194 CityView 91289 324-8909 pickpick 53335 The Candy Kid W 2121 Main St. 91212 563-4545 kidcandy 23516 Waterman, Al P 23 Yankee Blvd. 91234 w ateral 89007 Bobby Bon Bons R 12 Nichi Cres. 91212 434-9045 bobbybon 30118 Crow sh, Elias P 7 77th Ave. 91211 434-0007 crow el 10339 Montag, Susie P 981 Montview 91213 456-2091 montags 9633


Foreign Key Field that is a primary key in another table Used to create a relationship



Composite Key Primary key comprised of 2 or more fields


Review: Levels of data models1. Conceptual: describes WHAT data the

system contains2. Logical: describes HOW the database will

be structured, regardless of the DBMS3. Physical: describes HOW the system will be

implemented using a specific DBMS

Goal of Logical DB Design: Database Integrity

Entity integrityEvery record must have a unique primary keyThe primary key value cannot be NULL

Referential integrityEvery foreign key must be the primary key of

its parent tableEvery foreign key value must exist in its

parent table

Examples of Integrity ProblemsCUST_ID CUST_NAME CUST_TYPE CUST_ADDR CUST_ZIP CUST_PHONE USERNAME PASSWORD

1 Jones, Joe P 1234 Main St. 91212 434-1231 jonesj 12342 Armstrong,Inc. R 231 Globe Blvd. 91212 434-7664 armstrong 33333 Sw edish Burgers R 1889 20th N.E. 91213 434-9090 sw edburg 23534 Pickled Pickles R 194 CityView 91289 324-8909 pickpick 53335 The Candy Kid W 2121 Main St. 91212 563-4545 kidcandy 23516 Waterman, Al P 23 Yankee Blvd. 91234 w ateral 8900

Bobby Bon Bons R 12 Nichi Cres. 91212 434-9045 bobbybon 3011Crow sh, Elias P 7 77th Ave. 91211 434-0007 crow el 1033

9 Montag, Susie P 981 Montview 91213 456-2091 montags 963310 Columberg Sw eets W 239 East Falls 91209 874-9092 columsw e 8399



?

Steps for Transforming an ER Model into a Sound Logical Database Design

1. Create a table to represent every entity Entity PK is table PK

2. Represent each ER model relationship using foreign keys

Representing 1:M Relationships Put the PK of the “1” side into the “M” table

Dept_ID

Dept_Name Dept_Office_Loc

1 Accounting SSS415

2 IT SSS406

3 Production SSS312

Emp_ID

Emp_Last_Name

Emp_Office

Dept_ID (FK)

100 Smith SSS112 1

200 Jones SSS116 1

300 Brown SSS107 2

ACME_DEPARTMENT(Dept_ID, Dept_Name, Dept_Office_Loc)

ACME_EMPLOYEE(Emp_ID, Emp_Last_Name, Emp_Office, Dept_ID)

Why can’t you put the PK of the “M” side into the “1” table? A department has multiple employees…

Dept_ID

Dept_Name

Dept_Office

Emp_ID

1 Accounting SSS415 100, 200

2 MIS SSS406 300

3 Production SSS312

Dept_ID

Dept_Name

Dept_Office

Emp_ID

1 Accounting SSS415 100

1 Accounting SSS415 200

2 MIS SSS406 300

Approach 1: delimit multiple values using commas?Result: Non-relational tables (cell contains multiple values)

Approach 2: Repeat "1" side records for each "M" record?Result: Redundant data!

Representing M:M Relationships

Create a linking tableAlso called a bridge table

PK is a composite key comprised of PK’s of both entities in the M:M relationship

These fields are part of the PK, and are also FK’s

Representing M:M Relationships

Project_ID

Project_Name Project_Start_Date

1 Help Desk Intranet 01/05/12

2 Cold Fusion Study 01/15/12

3 Oracle Conversion 11/15/11

Emp_ID

Emp_Last_Name

Emp_Office

100 Smith SSS112

200 Jones SSS116

300 Brown SSS107

Project_ID (FK) Emp_ID (FK)

1 100

2 100

2 200

Project_ID (FK) Emp_ID (FK)

1 100

2 100

2 200

What do you name the linking table? Typically, a compound word comprised of

the two participating entities

ACME_EMPLOYEE_PROJECT

What about composite M:M relationships?

If the relationship has an attribute, place the attribute in the linking table

Project_ID (FK)

Emp_ID (FK) Emp_Proj_Hrs

1 100 30

2 100 15

2 200 25

Deriving Tables for 1:1 Relationships

In general, move one entity's non-key attributes into the other entity's table

ACME_EMPLOYEEEmp_IDEmp_Last_NameEmp_OfficeEmp_Spouse_FirstEmp_Spouse_Last

Deriving Tables for 1:1 Relationships How do you decide which entity to keep?

The "strong" entity Typically in a 1:1 relationship, one entity's instance

doesn't exist without the other's

Unary Relationships Treat just like any other 1:1, 1:M, or M:M

relationship, except modify key names to avoid duplicate field names

Student1_ID (FK)Student2_ID (FK)

ACME_EMPLOYEEEmployee_IDEmployee_First_NameEmployee_Last_NameEmployee_DOBSupervisorID (FK)

UWEC_STUDENT_ROOMS_WITH

Ternary Relationships Create a 3-way linking table

Student_ID (FK)Advisor_ID (FK)Program_ID (FK)

UWEC_STUDENT_ADVISOR_PROGRAM

Generalization/Specialization Create tables for the supertype and each of the

subtypes

Put PK of supertype into each subtype table as both a PK and FK

Generalization/SpecializationUWEC_PersonPerson_IDPerson_First_NamePerson_Last_NamePerson_MIPerson_DOB

UWEC_STUDENTPerson_ID (FK)Student_Major_ProgramStudent_Minor_Program

UWEC_INSTRUCTORPerson_ID (FK)Instructor_TitleInstructor_OfficeInstructor_Salary

UWEC_StaffPerson_ID (FK)Staff_RankStaff_Hourly_Rate

Supertype

Subtypes

Generalization/Specialization Data Table Example

Person_ID Person_First Person_Last Person_MI Person_DOB

100Joline Morrison P 7/14/1958

101Judith Mueller R. 8/12/1967

102Joshua Bates J. 2/15/1990

UWEC_PERSONPerson_ID Student_Major Student_Minor

102Graphic DesignWeb Development

UWEC_STUDENT

Person_IDInstructor_Title

Instructor_Office

Instructor_Salary

100Professor P 138 55000

UWEC_INSTRUCTOR

Person_ID Staff_RankStaff_Hourly_Rate

101Sr. Assoc. 21.55

UWEC_STAFF

Test Yourself: In the CANDY_PURCHASE table, PURCH_ID is an example of a:


a. A primary keyb. A foreign keyc. Part of a composite keya. Both b and cb. None of the above

CANDY_PURCHASE

Test Yourself: In the CANDY_PURCHASE table, PURCH_ID is an example of:


a. A primary keyb. A foreign keyc. Part of a composite keya. Both b and cb. None of the above

CANDY_PURCHASE

Test Yourself: In the CANDY_PURCHASE table, PROD_ID is an example of a:

a. Primary keyb. Foreign keyc. Part of a composite keyd. Both b and ce. None of the above


CANDY_PURCHASE

Test Yourself:How many database tables would you create for the following ER model?

a. 3b. 4c. 5d. None of the above

Your Turn #1 Derive the tables for the following ER model. Format the table

structures using the format TABLE_NAME(Field1, Field2, …). Underline primary key fields, and label foreign keys using the designation (FK).

Your Turn #1 SolutionALS_CUSTOMER(Customer_ID, Customer_Last_Name, Customer_First_Name,Customer_MI, Customer_Address, Customer _City, Customer_State, Customer_Zip,Customer_Phone)

ALS_CAR(Car_VIN, Car_Make, Car_Model,Car_Year, Customer_ID (FK))

ALS_WORK_ORDER (WO_ID, WO_Date,Car_VIN (FK))

ALS_SERVICE (Service_ID, Service_Name,Service_Desc, Service_Charge)

ALS_WORK_ORDER_SERVICE (Service_ID (FK), WO_ID (FK))

Your Turn #2 Derive the tables for the

following ER model. Format the table structures using the format TABLE_NAME(Field1, Field2, …). Label all primary keys by underlining them, and label foreign keys using the designation (FK).

Your Turn #2 Solution UWEC_PERSON(Person_ID,

Person_First_Name, Person_Last_Name, Person_MI, Person_Email)

UWEC_STUDENT(Person_ID (FK), Stu_Campus_Address, Stu_Campus_City, Stu_Campus_State, Stu_Campus_Zip, Stu_Campus_Phone, Stu_Perm_Address, Stu_Perm_City, Stu_Perm_State, Stu_Perm_Zip, Stu_Perm_Phone)

UWEC_INSTRUCTOR(Person_ID (FK), Instructor_Title, Instructor_Office, Instructor_Office_Phone)

UWEC_COURSE (Course_ID , Course_Dept, Course_Name, Course_Desc)

UWEC_COURSE_SECTION(Section_ID, Section_Term, Section_Day, Section_Time, Section_Location, Person_ID (FK), Course_ID (FK))

UWEC_STUDENT_COURSE_SECTION(Person_ID (FK), Section_ID (FK), Enrollment_Grade)

UWEC_ADVISOR (Student_Person_ID (FK), Instructor_Person_ID (FK))

database design 4: deriving tables from data models cs 320

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