Question

I have the following table below and am supposed to convert it to 2NF.

I have an answer to this where I have gone:

SKILLS: Employee, Skill

LOCATION: Employee, Current Work
Location

I have a feeling I’m wrong with this ^above^ though.

Also can someone explain what the differences are between 1NF, 2NF and 3NF. I know 1 comes first and you have to break it all up into smaller tables but would like a really good description to help me understand better. Thanks

Answer 1

Employee Table

EmployeeID  |   Name
1       |   Jones
2       |   Bravo
3       |   Ellis
4       |   Harrison


Skills Table

SkillId     |   Skill
1       |   Typing
2       |   Shorthand
3       |   Whittling
4       |   Light Cleaning
5       |   Alchemy
6       |   Juggling

Location Table

LocationId  |   Name
1       |   114 Main Street
2       |   73 Industrial Way

EmployeeSkill Table

EmployeeId  |   LocationId  |   SkillId |   SkillName
1       |   1       |   1   |   Typing
1       |   1       |   2   |   Shorthand
1       |   1       |   3   |   Whittling
2       |   2       |   4   |   Light Cleaning
3       |   2       |   5   |   Alchemy
3       |   2       |   6   |   Juggling
4       |   2       |   4   |   Light Cleaning

In the EmployeeSkill table the primary key would be EmployeeId + LocationId, this gives you the skill they have at that location. Including the SkillName column violates 3NF in this example.
This practice is actually used sometimes in database design (and called “denormalization”) in order to reduce joins to increase performance reading data that is commonly used together.
Ususally this is only done in tables used for reporting.