Question

I have a database design question.

In my application, a user has contact information including

• telephone number
• email
• adress line 1
• postal box
• Locality (City)

This is currentl located in a “user” table with the other informations like username, first name, …

The thing is that a user has to have the same kind of information (telephone, email, …) but for his company.

It seems redundant to add additional fields to the “user” table. As the data are similar, I could make a “ContactInfo” table with the fields:

• phone
• email
• address
• postal box
• …

Is it a good idea and how should I do the relation between the “user” table and this “contactInfo” table ?

EDIT: I forgot to say that the company contact information is not obligatory. A user can have no company at all.

Answer 1

Separate tables are the right choice.

CREATE TABLE users (
  id INT UNSIGNED NOT NULL,
  foo VARCHAR(50),
  PRIMARY KEY (id) );

CREATE TABLE user_contact_info (
  id INT UNSIGNED NOT NULL,
  user_id INT UNSIGNED NOT NULL,
  contact_type VARCHAR(40) NOT NULL,
  phone VARCHAR(20),
  email VARCHAR(200),
  address VARCHAR(200),
  postal_box VARCHAR(20),
  PRIMARY KEY (id, user_id) );

If your database supports foreign keys, there should be a foreign key from user_contact_info.user_id to users.id. user_contact_info.contact_type would be set to work or home or whatever other categories you need.