1. Hele-Mai Haav:
CSC210-Spring*01
CSC230-Spring*03
Database Design

2. The process of designing a database begins with an analysis of what information the database must hold and the relationships among components of that information.
The structure of the database is called the database schema and it is specified in one of database design languages (e.g. E/R or ODL)
If the design is committed to a form in which it can be put to a DBS, then the database takes physical existence

3. IDENTIFY RELATIONSHIPS
DATABASE DESIGN
IDENTIFY ENTITIES
IDENTIFY RELATIONSHIPS
CHECK FOR DESIGN PROBLEMS
SELECT PRIMARY KEYS
CREATE INITIAL RELATIONS
APPLY NORMALIZATION PRINCIPLES
PRODUCE FINAL DESIGN

4. UML
Object-oriented DBS
ODL
Ideas
Relations
Relational
DBS
E-R
Database modeling and implementation

5. Entity-Relationship Diagrams
Entity and entity sets
An entity set is a collection of distinguishable real-world objects with common properties. An entity is a member of an entity set
Students, Instructors, Cars...
Attributes
An attribute is a data item that describes a property of an entity or a relationship
name, registration number, rank….

6. Relationship
Relationships are connections among two or more entity sets
Multiplicity of E-R Relationships
many-to-one
many-to-many
one-to-one

7. name
addr
title
year
movies
Stars-in
Stars
length
filmtype
Owns
Studios
E-R schema of movie database
name
addr

8. Attributes on Relationships

9. E-R DIAGRAM S/W COMPANY SALES PERSON S/W PACKAGES REPRESENTS NAME
PHONE
RNO
ADDRESS
KEY
SALES PERSON
SSN
REGION 1 n
ONE-TO-MANY
DISTRIBUTES
PRICE
MANY-TO-MANY m
S/W PACKAGES
CODE
PURPOSE
E-R DIAGRAM

10. ONE-TO-MANY RELATIONSHIP
IBM MS
BCS
HELMES
LAURI
VERA
JAANUS
MERIKE
JUSTAS
S/W COMPANY
REPRESENTS
SALES PERSON

11. MANY-TO-MANY RELATIONSHIP
IBM MS
BCS
HELMES
OS/2
OFFICE 95
WIN NT
OFFICE 97
WIN 95
S/W COMPANY
DISTRIBUTES
S/W PACKAGES
LOTUS NOTES

12. Design Principles Faithfulness
Entity sets and their attributes should reflect reality
Whatever connections are asserted should make sense given what we know about the part of the real world being modeled

13. Avoiding Redundancy
We should be careful to say everything once only
Simplicity Counts
Avoid introducing more elements into your design than are absolutely necessary

14. Keys in E-R model
We underline the attributes belonging to a key for an entity set (primary key is indicated only)
title
year
movies

15. Relational Database =
set of RELATIONS (or TABLES) each with a distinct name
Movies, Stars,….
Each relation has a set of ATTRIBUTES (or COLUMNS) with a distinct name within its relation
title, year, length, filmtype,...

16. Relational data model is used by most commercial DBS
Oracle, Informix, Sybase, MS Access
Relational model is very simple

17. Keys:
A key for a relation is a set of attributes such that no two tuples can have the same values for all of their key attributes.
In real databases, if there isn't a natural, compact one-attribute
key, then keys may be system-generated.

18. Translating E-R design to relations
Assume each entity set has a specified key
Translation can be fully automated (except determining keys for generated relations in certain cases)

19. 1. Entity set (strong) translates directly to relation
SW Company
R-No Name Address Phone
R101 IBM Pirita tee
R102 Microsoft XYZ
R103 BCS Narva mnt
R104 Helmes Parnu mnt
R106 IE Soft Akadeemia tee

20. E-R Relationships translate to Relations
Corresponding relation has attribute for key attributes of each entity set (E. S.) that participates in relationship
if the relationship has attributes, then these are also attributes of corresponding relations
renaming attributes is OK (needed if multiple roles in one E. S.

21. 2. Binary relationship set between entity sets translates to relation containing keys for entity sets
RNO Code Price
R101 S
R101 S
R101 S
R101 s
R101 S
R101 S
R102 S
R102 S
R102 s
R103 S
R104 S
R106 S
R106 S
Distribution
Relationship set with attributes: add attributes to relation for relationship set

22. What is key for relation?
In most general case, key for the relation=
all key attributes from all the E.S. involved in relationship
however, the relation’s key excludes attributes from the “one” side if relationship is many-one
for one-to-one relationship, choose which side provides the key for the relation

23. Combining relations Foreign key Salespersons Common case
relation for an E.S. E plus the relation for some many-one relationship from E to another E.S.
Foreign key
Salespersons
SSN Name Region RNo
K10100 Lauri Estonia R104
K10150 Vera Estonia R103
K10200 Jaanus Latvia R104
K10300 Justas Lithuania R102
K10500 Merike Estonia R101
K10600 Marion Latvia R101
K20000 Margus Estonia R102
K Edgars Latvia R106

24. name
manuf
addr
name
beers
likes
drinkers
favorite
married
Example

25. Drinker(name,addr,….favoritebeerName)
beers(name, manuf)
likes(DrinkerName,BeerName)
married(hasbund,wife)

26. Example:Registration process at CIUE
Financial
Information
STUDENTS
REGISTRAR
Student Service
Office
BANK
ACCOUNTANT
Account Information
Registration Information
Special
Forms
Application 4
REGISTER 3
MANAGE
REGISTRATION
FORMS 2
SCHEDULE 1
MANAGE BILLS
Money
Receipts
Data
Pay
Registration
Chosen Courses
Course data