Normalizing a Sample Table

Unnormalized table:

EmployeeID	Director	DirectorRole	Skill1	Skill2	Skill3
1001	Brian	Technical	SQL	C++	.Net
1002	Victor	Institutional	People Mgmt.	Payroll Mgmt.	Knowledge Mgmt.

First Normal Form: No Repeating Groups
Tables should have only two dimensions. Since one employee has several skills, these skills should be listed in a separate table. Fields Skill1, Skill2, and Skill3 in the above records are indications of design trouble.

Spreadsheets often use the third dimension, but tables should not. Another way to look at this problem is with a one-to-many relationship, do not put the one side and the many side in the same table. Instead, create another table in first normal form by eliminating the repeating group (Skills), as shown below:

EmployeeID	Director	DirectorRole	Skills
1001	Brian	Technical	SQL
1001	Brian	Technical	C++
1001	Brian	Technical	.Net
1002	Victor	Institutional	People Mgmt.
1002	Victor	Institutional	Payroll Mgmt.
1002	Victor	Institutional	Knowledge Mgmt.

Second Normal Form: Eliminate Redundant Data
Note the multiple Skills values for each Employee value in the above table. Skill is not functionally dependent on EmployeeID (primary key), so this relationship is not in second normal form.
The following two tables demonstrate second normal form:

Employees

EmployeeID	Director	DirectorRole
1001	Brian	Technical
1002	Victor	Institutional

EmployeeSkills

EmployeeID	Skills
1001	SQL
1001	C++
1001	.Net
1002	People Mgmt.
1002	Payroll Mgmt.
1002	Knowledge Mgmt.

Third Normal Form: Eliminate Data Not Dependent On KeyIn the last example; DirectorRole is functionally dependent on the Director attribute. The solution is to move that attribute from the Employees table to the Directors table, as shown below:

Employees

EmployeeID	Director
1001	Brian
1002	Victor

Directors

Director	DirectorRole
Brian	Technical
Victor	Institutional