1

Normalisation

A2 ICT

2

The Data ProblemEquipment Service RecordItem Ref……10…………………… Location…Garage………………………Item Name……Buggy………………… Location Ext……1234……………Item Type……non-critical…………………….Purchase date…23/05/99…………………

Service ref Date of Work Tasks Required Tasks Performed Serviced By Date of Next Service Cost £

1 23/05/01 Grease wheels As required P.K. Jones 23/05/02 5.00

2 23/05/02 New bearings and general service

As required Kennedys 23/05/03 10.00

3 01/04/03 Brake test Brakes fixed P.K. Jones 23/05/03 20.00

Total Cost to date £35.00

3

Why do we normalise?

• Data duplication – wasting space

• Redundant data

• Same data held in several records/tables

• Data inconsistency – difficult to maintain

4

Step 1Equipment Service RecordItem Ref……10…………………… Location…Garage………………………Item Name……Buggy………………… Location Ext……1234……………Item Type……non-critical…………………….Purchase date…23/05/99…………………

Service ref Date of Work Tasks Required Tasks Performed Serviced By Date of Next Service Cost £

1 23/05/01 Grease wheels As required P.K. Jones 23/05/02 5.00

2 23/05/02 New bearings and general service

As required Kennedys 23/05/03 10.00

3 01/04/03 Brake test Brakes fixed P.K. Jones 23/05/03 20.00

Total Cost to date £35.00

a) This part of the form relates to the Item

b) This part of the form relates to the Service Records

We can see that one Item can have many

Service Records

5

Step 1

Item Ref

Item

Service Ref

Item Ref (FK)

Service Record

We have identified the first two entities from the record cards.

Add the Primary Keys and use a Foreign Key to link the two entities to identify the relationship.

6

Step 1

Item RefItem NameItem TypeLocationLocation ExtnPurchase Date

tbl_Item

Service RefTask RequiredTask PerformedDate of WorkDate next serviceItem Ref (FK)Serviced byCost

tbl_Service

We have identified the first two entities from the record cards.

Add the Primary Keys and use a Foreign Key to link the two entities to identify the relationship.

7

tbl_Itemtbl_Item (Item_Ref, Item_Name, Item_Type, Location, Location_Extn, Purchase_Date)

Item_Ref Item_Name Item_Type Location Location_Extn

Purchase_Date

10 Buggy Non-critical Garage 1234 23/05/99

21 Paintball Gun

Critical Shed 789 12/09/00

23 Deep Fryer Catering HQ 2222 03/07/00

35 Quad Bike Semi Critical

Garage 1234 09/08/99

54 Pool Car Vehicle Garage 1234 24/02/97

           

8

tbl_Itemtbl_Item (Item_Ref, Item_Name, Item_Type, Location, Location_Extn, Purchase_Date)

Item_Ref Item_Name Item_Type Location Location_Extn

Purchase_Date

10 Buggy Non-critical Garage 1234 23/05/99

21 Paintball Gun

Critical Shed 789 12/09/00

23 Deep Fryer Catering HQ 2222 03/07/00

35 Quad Bike Semi Critical

Garage 1234 09/08/99

54 Pool Car Vehicle Garage 1234 24/02/97

           

Repeats

9

Step 2

Item RefItem NameItem TypeLocation Ref (FK)Purchase Date

tbl_Item

We have created a new entity for the Location to remove the repeated fields from tbl_Item

A new field Location Ref has been created to link the two tables.

Location RefLocationLocation Extn

tbl_Location

10

tbl_Itemtbl_Item (Item_Ref, Item_Name, Item_Type, Location Ref, Purchase_Date)

Item_Ref Item_Name Item_Type Location_Ref Purchase_Date

10 Buggy Non-critical 1 23/05/99

21 Paintball Gun Critical 2 12/09/00

23 Deep Fryer Catering 3 03/07/00

35 Quad Bike Semi Critical 1 09/08/99

54 Pool Car Vehicle 1 24/02/97

         

11

tbl_Locationtbl_Location (Location_Ref, Location, Location_Extn)

Location_Ref Location Location_Exn

1 Garage 1234

2 Shed 789

3 HQ 2222

     

12

First Normal Form

• The data in our three tables can now be described as having been normalised to First Normal Form

• This means that all fields on every table are related to the Primary Key on that table

13

First Normal Form

Item RefItem NameItem TypeLocation Ref (FK)Purchase Date

tbl_Item

Location RefLocationLocation Extn

tbl_Location

tbl_Service

Service RefTask RequiredTask PerformedDate of WorkDate next serviceItem Ref (FK)Serviced byCost

14

Second Normal Form

• This data in also in Second Normal Form

• This means that all fields are related to the whole Primary Key – this stage of normalisation relates to entities with compound keys (where the primary key is made up of more than one field)

• This stage doesn’t affect our tables, all of which have a single primary key

15

Second Normal Form

Item RefItem NameItem TypeLocation Ref (FK)Purchase Date

tbl_Item

Location RefLocationLocation Extn

tbl_Location

tbl_Service

Service RefTask RequiredTask PerformedDate of WorkDate next serviceItem Ref (FK)Serviced byCost

16

Third Normal Form

• Third Normal Form requires the fields to be only related to the entity/table to which they belong

• If we look at our entities we can see that this is not the case

• The field Serviced_by relates to an external entity which should have attributes of its own

17

tbl_Servicetbl_Service (Service_Ref, Date_of_Work, Item_Ref, Task_Required, Task_Done, Serviced_by, Date_next_service, Cost) 1 23/05/01

10 Grease wheels As req’d P. K. Jones 23/05/02 5.00

2 23/05/02

10 New bearings and general service

As req’d Kennedy’s 23/05/03 10.00

3 01/04/03

10 Brake test Brakes fixed P. K. Jones 23/05/04 20.00

4 12/02/01

21 Routine check As req’d JD Gasses 12/02/01 5.00

5 10/02/01

21 Routine check Re gassed PK Jones 10/05/03 6.00

6 10/04/03

21 Barrel block unblock PK Jones 10/05/03 7.00

7 03/09/00

23 Change fuse As req’d Kennedys 03/10/00 5.00

8 03/10/00

23 Change fat Change fat & scrub JD Gasses 03/01/01 10.00

9 09/02/00

35 Routine service Plugs & oil Yale Motors

02/10/00 55.00

10 30/09/00

35 Routine service Plugs & oil & fan belt Yale Motors

30/3/01 60.00

11 26/02/97

54 Re-start New fuses Kennedys 24/02/98 20.00

12 22/02/98

54 Service As required Yale Motors

22/02/99 30.00

13 22/02/99

54 Major Service As required new tyres also

Yale Motors

22/02/00 300.00

This can cause several problems with

the data being held

18

tbl_Servicetbl_Service (Service_Ref, Date_of_Work, Item_Ref, Task_Required, Task_Done, Serviced_by, Date_next_service, Cost) 1 23/05/01

10 Grease wheels As req’d P. K. Jones 23/05/02 5.00

2 23/05/02

10 New bearings and general service

As req’d Kennedy’s 23/05/03 10.00

3 01/04/03

10 Brake test Brakes fixed P. K. Jones 23/05/04 20.00

4 12/02/01

21 Routine check As req’d JD Gasses 12/02/01 5.00

5 10/02/01

21 Routine check Re gassed PK Jones 10/05/03 6.00

6 10/04/03

21 Barrel block unblock PK Jones 10/05/03 7.00

7 03/09/00

23 Change fuse As req’d Kennedys 03/10/00 5.00

8 03/10/00

23 Change fat Change fat & scrub JD Gasses 03/01/01 10.00

9 09/02/00

35 Routine service Plugs & oil Yale Motors

02/10/00 55.00

10 30/09/00

35 Routine service Plugs & oil & fan belt Yale Motors

30/3/01 60.00

11 26/02/97

54 Re-start New fuses Kennedys 24/02/98 20.00

12 22/02/98

54 Service As required Yale Motors

22/02/99 30.00

13 22/02/99

54 Major Service As required new tyres also

Yale Motors

22/02/00 300.00

Repeated data

19

tbl_Servicetbl_Service (Service_Ref, Date_of_Work, Item_Ref, Task_Required, Task_Done, Serviced_by, Date_next_service, Cost) 1 23/05/01

10 Grease wheels As req’d P. K. Jones 23/05/02 5.00

2 23/05/02

10 New bearings and general service

As req’d Kennedy’s 23/05/03 10.00

3 01/04/03

10 Brake test Brakes fixed P. K. Jones 23/05/04 20.00

4 12/02/01

21 Routine check As req’d JD Gasses 12/02/01 5.00

5 10/02/01

21 Routine check Re gassed PK Jones 10/05/03 6.00

6 10/04/03

21 Barrel block unblock PK Jones 10/05/03 7.00

7 03/09/00

23 Change fuse As req’d Kennedys 03/10/00 5.00

8 03/10/00

23 Change fat Change fat & scrub JD Gasses 03/01/01 10.00

9 09/02/00

35 Routine service Plugs & oil Yale Motors

02/10/00 55.00

10 30/09/00

35 Routine service Plugs & oil & fan belt Yale Motors

30/3/01 60.00

11 26/02/97

54 Re-start New fuses Kennedys 24/02/98 20.00

12 22/02/98

54 Service As required Yale Motors

22/02/99 30.00

13 22/02/99

54 Major Service As required new tyres also

Yale Motors

22/02/00 300.00

Inconsistencies

20

Step 3

Item RefItem NameItem TypeLocation Ref (FK)Purchase Date

tbl_Item

We have created a new entity for the Servicer, tbl_Service

A new field Servicer_ID has been created to link the two tables. We can now add the other fields that we were given relating to this new entity

Location RefLocationLocation Extn

tbl_Location

tbl_Service

Service RefTask RequiredTask PerformedDate of WorkDate next serviceItem Ref (FK)Servicer_ID (FK)Cost

Servicer_IDServicer NameContactPhone NumberAddress

tbl_Servicer

21

tbl_Servicetbl_Service (Service_Ref, Date_of_Work, Item_Ref, Task_Required, Task_Done, Servicer_ID, Date_next_service, Cost)

1 23/05/01

10 Grease wheels As req’d 1 23/05/02 5.00

2 23/05/02

10 New bearings and general service

As req’d 2 23/05/03 10.00

3 01/04/03

10 Brake test Brakes fixed 1 23/05/04 20.00

4 12/02/01

21 Routine check As req’d 3 12/02/01 5.00

5 10/02/01

21 Routine check Re gassed 1 10/05/03 6.00

6 10/04/03

21 Barrel block unblock 1 10/05/03 7.00

7 03/09/00

23 Change fuse As req’d 2 03/10/00 5.00

8 03/10/00

23 Change fat Change fat & scrub 3 03/01/01 10.00

9 09/02/00

35 Routine service Plugs & oil 4 02/10/00 55.00

10 30/09/00

35 Routine service Plugs & oil & fan belt 4 30/3/01 60.00

11 26/02/97

54 Re-start New fuses 2 24/02/98 20.00

12 22/02/98

54 Service As required 4 22/02/99 30.00

13 22/02/99

54 Major Service As required new tyres also

4 22/02/00 300.00

22

tbl_Servicertbl_Servcier (Servicer_ID, Servicer_Name, Contact, Phone No, Address)

Servicer_ID Servicer_Name

Contact Phone Number

Address

1 P. K. Jones Robert Smith 88888888888 3, High Road, Mold, MO6 5DF

2 Kennedy’s Big Phil 123456789 Big Street, Wrexham LL34 2PQ

3 J D Gasses Gassy John 11111111111 33, Main Road, Chester, CH6 9LK

4 Yale Motors Mike Jones 54545454 Grove Park Road, Wrexham LL34 5BG

23

Third Normal Form

Item RefItem NameItem TypeLocation Ref (FK)Purchase Date

tbl_Item

Location RefLocationLocation Extn

tbl_Location

tbl_Service

Service RefTask RequiredTask PerformedDate of WorkDate next serviceItem Ref (FK)Servicer_ID (FK)Cost

Servicer_IDServicer NameContactPhone NumberAddress

tbl_Servicer

24

System improvements

Item RefItem Name

Location Ref (FK)Purchase DateType_Ref (FK)

tbl_Item

Location RefLocationLocation Extn

tbl_Location

tbl_Service

Service RefTask RequiredTask PerformedDate of WorkDate next serviceItem Ref (FK)Servicer_ID (FK)Cost

Servicer_IDServicer NameContactPhone NumberAddress

tbl_Servicer

Type_RefItem_TypeService_Interval

tbl_Type

25

tbl_Itemtbl_Item (Item_Ref, Item_Name, Type_Ref, Location Ref, Purchase_Date)

Item_Ref Item_Name Type_Ref Location_Ref Purchase_Date

10 Buggy N 1 23/05/99

21 Paintball Gun C 2 12/09/00

23 Deep Fryer K 3 03/07/00

35 Quad Bike S 1 09/08/99

54 Pool Car V 1 24/02/97

         

26

tbl_Typetbl_Type (Type_Ref, Item_Type, Service Interval)

Type_Ref Item_Type Service_Interval

N Non Critical 12

C Critical 3

K Catering 3

S Semi Critical 6

V Vehicle 12

27

How does this help?

• Can automatically calculate next service dates

• Can easily change service intervals if necessary

• Can add extra categories when required