1. Database Design 4: Deriving Tables From Data Models CS 320

2. Review: Relationships in Tables Created by shared key fields

3. Types of Database Key Fields Primary keys Foreign keys Composite keys

4. 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

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

6. Composite Key Primary key comprised of 2 or more fields

7. Review: Levels of data models 1. Conceptual: describes WHAT data the system contains 2. Logical: describes HOW the database will be structured, regardless of the DBMS 3. Physical: describes HOW the system will be implemented using a specific DBMS

8. Goal of Logical DB Design: Database Integrity Entity integrity  Every record must have a unique primary key  The primary key value cannot be NULL Referential integrity  Every foreign key must be the primary key of its parent table  Every foreign key value must exist in its parent table

9. Examples of Integrity Problems ?

10. 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

11. Representing 1:M Relationships Put the PK of the “1” side into the “M” table Dept_ ID Dept_NameDept_Office_ Loc 1AccountingSSS415 2ITSSS406 3ProductionSSS312 Emp_ ID Emp_ Last_ Name Emp_ Office Dept_ ID (FK) 100SmithSSS1121 200JonesSSS1161 300BrownSSS1072 ACME_DEPARTMENT(Dept_ID, Dept_Name, Dept_Office_Loc) ACME_EMPLOYEE(Emp_ID, Emp_Last_Name, Emp_Office, Dept_ID)

12. 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 1AccountingSSS415100, 200 2MISSSS406300 3ProductionSSS312 Dept_ ID Dept_ Name Dept_ Office Emp_ ID 1AccountingSSS415100 1AccountingSSS415200 2MISSSS406300 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!

13. Representing M:M Relationships Create a linking table  Also 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

14. Representing M:M Relationships Project_ ID Project_NameProject_ Start_ Date 1Help Desk Intranet01/05/12 2Cold Fusion Study01/15/12 3Oracle Conversion11/15/11 Emp_ ID Emp_Last _Name Emp_ Office 100SmithSSS112 200JonesSSS116 300BrownSSS107 Project_ID (FK)Emp_ID (FK) 1100 2 2200

15. Project_ID (FK)Emp_ID (FK) 1100 2 2200 What do you name the linking table? Typically, a compound word comprised of the two participating entities ACME_EMPLOYEE_PROJECT

16. 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 110030 210015 220025

17. Deriving Tables for 1:1 Relationships  In general, move one entity's non-key attributes into the other entity's table ACME_EMPLOYEE Emp_ID Emp_Last_Name Emp_Office Emp_Spouse_First Emp_Spouse_Last

18. 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

19. 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_EMPLOYEE Employee_ID Employee_First_Name Employee_Last_Name Employee_DOB SupervisorID (FK) UWEC_STUDENT_ROOMS_WITH

20. Ternary Relationships Create a 3-way linking table Student_ID (FK) Advisor_ID (FK) Program_ID (FK) UWEC_STUDENT_ ADVISOR_PROGRAM

21. 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

22. Generalization/Specialization UWEC_Person Person_ID Person_First_Name Person_Last_Name Person_MI Person_DOB UWEC_STUDENT Person_ID (FK) Student_Major_Program Student_Minor_Program UWEC_ INSTRUCTOR Person_ID (FK) Instructor_Title Instructor_Office Instructor_Salary UWEC_Staff Person_ID (FK) Staff_Rank Staff_Hourly_Rate Supertype Subtypes

23. Generalization/Specialization Data Table Example Person_ IDPerson_FirstPerson_LastPerson_MIPerson_DOB 100JolineMorrisonP7/14/1958 101JudithMuellerR.8/12/1967 102JoshuaBatesJ.2/15/1990 UWEC_PERSON Person_IDStudent_MajorStudent_Minor 102Graphic Design Web Development UWEC_STUDENT Person_ID Instructor_ Title Instructor_ Office Instructor_ Salary 100ProfessorP 13855000 UWEC_INSTRUCTOR Person_IDStaff_Rank Staff_Hourly_ Rate 101Sr. Assoc. 21.55 UWEC_STAFF

24. Test Yourself: In the CANDY_PURCHASE table, PURCH_ID is an example of a: a. A primary key b. A foreign key c. Part of a composite key a. Both b and c b. None of the above CANDY_PURCHASE

25. Test Yourself: In the CANDY_PURCHASE table, PURCH_ID is an example of: a. A primary key b. A foreign key c. Part of a composite key a. Both b and c b. None of the above CANDY_PURCHASE

26. Test Yourself: In the CANDY_PURCHASE table, PROD_ID is an example of a: a. Primary key b. Foreign key c. Part of a composite key d. Both b and c e. None of the above CANDY_PURCHASE

27. Test Yourself: In the CANDY_PURCHASE table, PROD_ID is an example of a: a. Primary key b. Foreign key c. Part of a composite key d. Both b and c e. None of the above CANDY_PURCHASE

28. Test Yourself: How many database tables would you create for the following ER model? a. 3 b. 4 c. 5 d. None of the above

29. Test Yourself: How many database tables would you create for the following ER model? a. 3 b. 4 c. 5 d. None of the above

30. 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).

31. Your Turn #1 Solution ALS_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))

32. 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).

33. 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))