CS 3630 Database Design and Implementation

Unnormalized Form (UNF)

student courses

John CS363

CS334

CS323

• Multi-Value attribute

• Common in reports

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First Normal Form (1NF)

• No multi-value attributes

• Done when mapping E-R model to relational schema

• DBDL

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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 FDs on the PK.

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5

Partial FDs

X, Y W is partial (W partially depends on X or Y) if

X W or Y W is true

Example:

Sno, Bno staffAddress, staffPhone staffAddress and staffPhone are Partially depend on Sno,

since the following is true

Sno staffAddress, staffPhone

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Full FDs

A FD is a full FD if it’s not partial.

A, B X, Y is a full FD if both of the following are false: A X, Y B X, Y

Sno staffAddress, staffPhone

Cannot be partial!

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Full FDs

A FD is a full FD if it’s not partial.

Pno, Start Rno, Rent, Finish

Both of the following are false: Pno Rno, Rent, Finish Start Rno, Rent, Finish

Second Normal Form (2NF) No Partial FDs on the PK.

PK ---> All other attributes

Assume a table with a simple PK of Att1

Att1 ---> All other attributes

Cannot have partial FD on simple PK

Assume a table with a composite PK of Att1 and Att2

Att1, Att2 ---> Att3, Att4, Att5 (All other attributes)

It’s possible

Att2 ---> Att5

Att1, Att2 ---> Att3, Att48

ExampleLease (RNo, RName, PNo, PAddress, Start, Finish, Rent, ONo, OName)

PK: PNo, Start

AK: PNo, Finish

PAddress, Start

PAddress, Finish

FDs:

PNo, Start ---> All

PNo, Finish ---> All

PAddress, Start ---> All

PAddress, Finish ---> All

RNo ---> RName

ONo ---> Oname

PAddress ---> PNo, ONo, OName

PNo ---> PAddress, ONo, OName (Partial on Primary Key)

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Table Instance RNo RName PNo PAddress Start Finish Rent Ono OName R101 John P1001 1001 main 1-1-04 12-31-04 350 O100 Tina R102 Mike P1001 1001 main 1-1-05 2-28-05 380 O100 Tina R103 Kay P1001 1001 main 3-1-05 12-31-05 380 O100 Tina R101 John P1002 2001 main 1-1-05 12-31-05 550 O110 Tony R105 Scot P1009 1009 first 1-1-04 5-31-04 350 O109 Tony

PNo, Start ---> All other attributes

(Partial on Primary Key) PNo ---> PAddress, ONo, OName

Not in 2NF!

Poor Performance Redundancy Inconsistency

What to Do?New Table!

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Decompose Lease into 2NF Lease (RNo, RName, PNo, PAddress, Start, Finish, Rent, ONo, OName) PK: PNo, Start Partial FD on Primary Key PNo ---> PAddress, ONo, OName

Remove partial dependent on Primary KeyCreate a new relationWhich attributes are in the new relation? All attributes in the partial FD (both side of) Lease1 (PNo, PAddress, ONo, OName)

Which attributes are left in the original relation? PK remains the same Lease2 (RNo, RName, PNo, Start, Finish, Rent)

PK and FK?11

Lease1 (PNo, PAddress, ONo, OName)

PK: PNo

AK: PAddress

FK: None (from this conversion

Functional Dependencies:

PNo ---> All other attributes

PAddress ---> PNo, ONo, OName

ONo ---> OName

In 2NF?

Lease2 (RNo, RName, PNo, Start, Finish, Rent)

PK: PNo, Start

AK: PNo, Finish

FK: PNo references Lease1

Functional Dependencies:

PNo, Start ---> All other attributes

PNo, Finish ---> All other attributes

RNo ---> Rname

In 2NF? 12

Relation/Table Instances Lease

Rno RName PNo PAddress Start Finish Rent Ono OName R101 John P1001 1001 main 1-1-04 12-31-04 350 O100 Tina R102 Mike P1001 1001 main 1-1-05 2-28-05 380 O100 Tina R103 Kay P1001 1001 main 3-1-05 12-31-05 380 O100 Tina R101 John P1002 2001 main 1-1-05 12-31-05 550 O110 Tony R105 Scot P1009 1009 first 1-1-04 5-31-04 350 O109 Tony

Lease1 PNo PAddress ONo OName P1001 1001 main O100 Tina P1001 1001 main O100 Tina P1001 1001 main O100 Tina P1002 2001 main O110 Tony P1009 1009 first O109 Tony

Lease1 = PNo, PAddress, Ono, OName (Lease)

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Removing Duplicates Lease1

PNo PAddress ONo OName P1001 1001 main O100 Tina P1001 1001 main O100 Tina P1001 1001 main O100 Tina P1002 2001 main O110 Tony P1009 1009 first O109 Tony

Lease1 P1001 1001 main O100 Tina P1002 2001 main O110 Tony P1009 1009 first O109 Tony

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Lease RNo RName PNo PAddress Start Finish Rent Ono

OName R101 John P1001 1001 main 1-1-04 12-31-04 350 O100 Tina R102 Mike P1001 1001 main 1-1-05 2-28-05 380 O100 Tina R103 Kay P1001 1001 main 3-1-05 12-31-05 380 O100 Tina R101 John P1002 2001 main 1-1-05 12-31-05 550 O110 Tony R105 Scot P1009 1009 first 1-1-04 5-31-04 350 O109 Tony

Lease2 RNo RName PNo Start Finish Rent R101 John P1001 1-1-04 12-31-04 350 R102 Mike P1001 1-1-05 2-28-05 380 R103 Kay P1001 3-1-05 12-31-05 380 R101 John P1002 1-1-05 12-31-05 550 R105 Scot P1009 1-1-04 5-31-04 350

Lease2 = RNo, RName, RNo, Start, Finish, Rent (Lease)

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Some FDs are lost

Lease (RNo, RName, PNo, PAddress, Start, Finish, Rent, ONo, OName)

PAddress, Start ---> All other attributes

PAddress, Finish ---> All other attributes

Lease1 (PNo, PAddress, ONo, OName)

Lease2 (RNo, RName, PNo, Start, Finish, Rent)

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Example

Relation R (A, B, C, D, E, F)

PK: A, B

AK: None

FK: None

Functional Dependencies:

A, B ---> All

A ---> C

B ---> E, F

In 2NF?

NO!

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Table Instance

A B C D E F

1 x 10 100 cs se

1 y 10 200 cs ee

2 x 20 300 cs se

2 y 20 400 cs ee

Functional Dependencies:

A, B ---> All

A ---> C

B ---> E, F

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R1 (A, C) Primary Key: A Alternate Key: None Foreign Key: None Functional Dependencies: A ---> C

R2 (B, E, F) Primary Key: B Alternate Key: None Foreign Key: None Functional Dependencies: B ---> E, F

R3 (A, B, D) Primary Key: A, B Alternate Key: None Foreign Key: A References R1 B References R2 Functional Dependencies: A, B ---> D 19

R (A, B, C, D, E, F)

Functional Dependencies: A, B ---> All A ---> C B ---> E, F

Decompose table R into 2NF

Table Instance

R

A B C D E F

1 x 10 100 cs se

1 y 10 200 cs ee

2 x 20 300 cs se

2 y 20 400 cs ee

R1

A C

1 10

2 20

R2

B E F

x cs se

y cs ee

R3

A B D

1 x 100

1 y 200

2 x 300

2 y 40020

Schedule

Assignment 5-1

Due Wednesday

Assignment 6-1

Due Monday, March 2

Quiz 2

Friday, March 621