FEN 2015-09-03 1

Introduction to the database field:

• The development process

Seminar:Introduction to relational databases

Development process:

• Analyse the problem domain and build a conceptual model (ER model)

• Table design

• Domains

• Primary key, foreign keys, constraints

• Quality checking design (normalisation)

• Create tables

• Run queries

2

Development Process

Analyse the problem domain:Identify:• entities • relations

FEN 2015-09-03

3

Development Process

FEN 2015-09-03

Build the conceptual model:• Attributes• Primary keys• Cardinality• Participation

4

Development ProcessTransform the ER model into relational schemas (tables):• 7 steps algorithm:

• Entity -> Table(composite, and multi value attributes)

• Weak entity -> Table(composite key, include owners key)

• 1-1 and 1-n relations(include primary key from one side as foreign key on the other side)

• n-m relations(new table with the primary keys from both sides as foreign keys, composite primary key)

• Multi value attributes - > new table(include the owners primary key as foreign key)

• Relations with degree > 2 -> new table(include all participants primary keys as foreign keys, composite primary key)

FEN 2015-09-03

5

Development Process

Result:

FEN 2015-09-03

6

Development Process

FEN 2015-09-03

Informal Design Guidelines: • Table Semantics• Avoid Redundant Information• Minimise NULL-values• Disallowing the generation of

spurious tuples when joining tables.Normalisation:• 1NF• 2NF• 3NF• BCNF• Look for functional

dependencies / determinants that are not keys

Not in

3NF!

Not in

2NF!

7

Development Process

FEN 2015-09-03

Guideline for Normalisation

All attributes are to depend on the key,the whole key,

and nothing but the key.So help me Codd.

And remember:• FDs are business rules• Normalisation fights redundancy and other maladies in table design

8

Development Process

Table definitions:• Data types (domains)• NULLs allowed?• Primary key (ids?)• Referential constraints (FK-PK references)

FEN 2015-09-03

Constraint

9

Development Process

Execute queries:• SELECT, INSERT, UPDATE, DELETE

FEN 2015-09-03

SELECT: Rows and columns Joins Set operations

10

Do it yourself

If you want to try it your self, you may want to install the free Microsoft SQL Server Express:

SQLServerInstall.pptx

FEN 2015-09-03

11

The End!Thank you very much – hope you liked it.

(fen@ucn.dk, http://public.ucn.dk/fen/angers/)

FEN 2015-09-03