I am trying to convert the schema of this database up to 3NF. As a first step, I figured it was in 0NF due to telephone numbers. I am confused what is the most efficient method to obtain 1NF.
employer(employer_id, skill, name, telephone_numbers, postal_code)
Having attempted the following :
employer(employer_id, skill, name, telephone_numbers, postal_code)
contact(employer_id, skill, telephone_numbers)
I do not believe this gets me anywhere does it?
make a table as the one you have but remove the telephone_numbers field. You then will have to have another table with telephone numbers and an which references the employer_id of the first table. If you want to allow for maximum adaptability (they may have a different contact phone number for cleaning services as for typing), you will need to reference a composite key not just the employer_id. For example; Employer_id + skill.
This will take you to 1NF.
To get to 3NF you will need to take skill out of both tables and reference it, you can also take the name and address info into separate tables.