Data analysis | Database

Normalisation - First normal form

1NF

Applicable when: Key field and related fields repeat.
Method:
1. Remove repeating groups
2. Identify entities by splitting into separate tables (entities).
3. Assign primary keys for each entity.

Example1:

EmpId	Name	Address	Course	Result
9012	Laurie Driver	12 Truck St	Turning	A
9012	Laurie Driver	12 Truck St	Braking	B
9012	Laurie Driver	12 Truck St	Parking	A
9122	Percy Vere	43 Tryhard Rd	Turning	B
9122	Percy Vere	43 Tryhard Rd	Parking	C
9823	Mike Robe	12 Small Cres	Parking	B

Step 1: Remove repeating data.

EmpId	Name	Address	Course	Result
9012	Laurie Driver	12 Truck St	Turning	A
			Braking	B
			Parking	A
9122	Percy Vere	43 Tryhard Rd	Turning	B
			Parking	C
9823	Mike Robe	12 Small Cres	Parking	B

Steps 2 & 3: Identify entities by splitting into separate tables (projection), and assign primary keys.

EmpId	Name	Address
9012	Laurie Driver	12 Truck St
9122	Percy Vere	43 Tryhard Rd
9823	Mike Robe	12 Small Cres

EmpId	Course	Result
9012	Turning	A
9012	Braking	B
9012	Parking	A
9122	Turning	B
9122	Parking	C
9823	Parking	B

Note : Normalised records may have concatenated keys (eg. EmpId + Course), if necessary to uniquely identify record.

[Rev 17/05/99] 13/6/97 © 1997-99 V/2-Com (Verhaart), P O Box 8415, Havelock North, New Zealand.