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CS 3630 Database Design and

Implementation

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Sets

Foundation of relational database.

Basic Operations

Power set

Mapping

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Relational Algebra Operations

• Selection• Projection• (Union)• (Set difference)• (Intersection)• Cartesian product• Join

Natural Join

Outer Join

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Relational Algebra Operations

• Apply to relation/table instances

• The result is still a relation/table instance

• Syntax

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Relational Algebra Operations

• Which tables?

• Which operations?

• Which common attribute for join?

• Which attributes to retrieve?

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(Guest Booking Hotel)

Guest.*

(fromDate <= CurrentDate and toDate >= CurrentDate and hotelName = ‘Grosvenor’)

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Design MethodologyA structured approach that uses procedures, techniques, tools, and

documentation aids to support and facilitate the process of design.

Three main phases 1. Conceptual database design E-R Model

2. Logical database design Mapping E-R Model to (relational) database schema Normalization

3. Physical database design

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E-R Model• Entity Attributes: Simple or Composite Single-value or Multi-value Required or optional

• Relationship One-to-One One-to-Many Many-to-Many Could have attributes

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Multiplicity

For one object on the other side!

E1 (1..1) IsRelatedTo (0..1) E2

E1 (0..*) IsRelatedTo (1..1) E2

E1 (0..*) IsRelatedTo (1..*) E2

Staff (1..*) IsRelatedTo (0..1) Branch

Renter (0..*) Views (0..*) Property

Date, Comment

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Mapping Entity

Composite AttributeDo we need a new table?

NO!

Multi-value AttributeDo we need a new table?

YES!

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Mapping Relationships

• One-to-Many Do we need a new table? NO!• One-to-One Do we need a new table? NO!• Many-to-Many Do we need a new table? YES!

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Table

Table Schema

Definition

DBDL

Do not change too often

Table Instance

Records stored in database

Different at different times

Candidate keys

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Candidate Key

A minimum set of attributes that uniquely identifies each record of a table.

No proper subset satisfying the definition.

R (Att1, Att2, Att3) Candidate Keys: (Att1, Att2) Either Att1 or Att2 is not a candidate key But Att3 could be a candidate key

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Candidate KeyA minimum set of attributes that uniquely identifies each

record of a table. No proper subset satisfying the definition.

R (Att1, Att2, Att3, Att4) Candidate Keys: (Att1, Att2) Att3

Functional Dependency Att3 All other attributes Att1, Att2 All other attributes

Att1 All other attributes Not True Att2 All other attributes Not True

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Candidate Key, PK, AK and FK

• A table could have more than one candidate key.

• One candidate key is selected as the primary key (PK).

• Other candidate keys become alternate keys (AK).

• PK can be copied to other tables as foreign keys (FK).

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Functional Dependency

Definition

In a relation/table R S: a set of attributes T: a set of attributes S T For ANY relation instance If two records of R have the same values on S Then they will have the same values on T

Trivial FDs A A A, B, C B, C

First Normal Form (1NF)

• No multi-value attributes

• Done when mapping E-R model to relational schema

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Second Normal Form (2NF)

A relation R is in 1NF, and

every non-primary-key attribute is fully functionally dependent on the primary key

Then R is in 2NF.

No Partial FD on PK.

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Third Normal Form (3NF)

Relation R in 2NF, and

No non-Primary-Key attribute is transitively functionally dependent on the primary key

Then R is in 3NF.

No Transitive FD on PK.

Must be in 2NF!19

Boyce-Codd Normal Form (BCNF)

Definition

R in 1NF and

Every determinant (the left side of a FD) is a candidate key.

Stronger than 3NF!

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Test 1: 50 Points• Wednesday• Lab 206• Sets• Relational Database Model• Relational Algebra• Mapping E-R model to table schema• Functional Dependency• Normalization• Open Book, Notes, Computer• Copy-paste word document

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Quiz2

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Assignment6-2

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Schedule

• Wednesday

Test1

• Friday

Assignment7

(Due 5 pm Friday)

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