1. CSIS 115 Database Design and Applications for Business
Dr. Meg Fryling
“Dr. Meg”
Fall 2012
@SienaDrMeg
#csis115

2. Agenda Homework (see next slide)
Chapter 6: Translating ER Diagrams to Relations
Conceptual design to physical database

3. Homework See Course Schedule for Readings Project – Part II (Rewrite)
Due Weds, 10/31 by start of class
Updated ER Diagram and any needed changes to description
Midterm is Mon, 11/5
Will discuss format as we get closer
May bring a “cheat sheet”
8.5x11, handwritten, both sides, must use your own!

4. FYI - Improve data entry by adding a lookup
Try it!
Add lookup so the only values that can be selected for company county are:
Schenectady
Albany
Hamilton

5. The ideal primary key is _____.
A) short
B) numeric
C) fixed
D) A and B
E) A, B and C
Answer: E

6. A surrogate key should be considered when ________.
A) a relationship is M:N
B) a composite key is required
C) the key contains a lengthy text field
D) the key contains a value that will change frequently
D) the key contains a number
Answer: C & D are best answers but B is a good answer too, particularly if the composite key contains more than 3-4 fields

7. Which of the following is not true about surrogate keys?
A) They are identifiers that are supplied by the system, not the users.
B) In Access, their data type is always Autonumber.
C) They are nonunique within a table.
D) The DBMS will not allow their values to be changed.
Answer: C

8. Surrogate Keys

9. In a relational database design, all relationships are expressed by ________.
A) creating a primary key
B) creating a foreign key
C) creating a supertype
D) creating a surrogate key
E) creating a line between entities
Answer: B
For weak ID-dependent entities, the foreign key is part of the primary key.

10. When representing a 1:1 relationship in a relational database design ________.
A) the key of each table must be placed as foreign keys into the other
B) the key of either table may be placed as a foreign key into the other
C) the key of both tables must be the same
D) the intersection table gets the key from both relations
E) B and C
Answer: B
As for C – The key of both tables could be the same but it is not required.

11. Which of the following is required to implement a 1:1 relationship?
Set foreign key to required
Index foreign key and allow duplicates
Index foreign key and do not allow duplicates
Make foreign key the primary key as well
No can do!
Answer: Both C and D will work

12. A) incremental updates B) incremental deletes
A referential integrity constraint policy that insures that foreign key values in a table are correctly maintained when there is a change to the primary key value in the parent table is called ________.
A) incremental updates
B) incremental deletes
C) controlled key adjustments
D) cascading updates
E) cascading deletes
Answer: D

13. Referential Integrity
Select for all relationships to maintain integrity of your data
Prevents orphan child records
Prevents entry of invalid values
Prohibit PK updates of parent OR cascade updates
No need with surrogate keys
Prohibit delete of parents (with child records) OR cascade deletes
Only cascade deletes on weak entities!
Prevents orphan child records (e.g. Won’t let me delete a Department if there are associated employees)
Prevents entry of invalid values (e.g. Associate employee with department that doesn’t exist in department table)

14. Which of these should I select?

15. WARNING: Must be same data type or you can’t enforce referential integrity

16. But remember… Foreign keys can never be autonumbers!!
If mapping to an autonumber primary key, select number data type.

17. What’s wrong here?
All fields in PK of patient must be FK in visit. The primary key of PATIENT should really just be PatientID.

18. Let’s Try It!
Open the HR Database from Blackboard (In-class activity 5)
This is not the same one you were creating!
HumanResourcesDB.accdb
Create relationship below

19. To represent a one-to-many relationship in a relational database design ________.
A) the key of the child is placed as a foreign key into the parent
B) the key of the parent is placed as a foreign key into the child
C) an intersection table must be created
D) the key of the table on the "many" side is placed in the table on the "one" side
E) the keys of both tables are joined into a composite key
Answer: B

20. Create Relationships: 1:N Strong Entity Relationships
KROENKE AND AUER - DATABASE PROCESSING, 11th Edition © 2010 Pearson Prentice Hall

21. Let’s Try It! Back to HR Database
Create a one-to-many “has-departments” relationship between COMPANY and DEPARTMENT

22. Relationships Using ID-Dependent Entities: Association Relationships
QUOTATION (CompanyName, PartNumber, Price)
KROENKE AND AUER - DATABASE PROCESSING, 11th Edition
© 2010 Pearson Prentice Hall

23. Relationships Using ID-Dependent Entities: Multivalued Attributes
As a data model
As a database design
KROENKE AND AUER - DATABASE PROCESSING, 11th Edition © 2010 Pearson Prentice Hall

24. Let’s Try It! Back to HR Database
Create a one-to-many “has-contacts” relationship between COMPANY and PHONE_CONTACT