Question

I want to create a small invoicing application. My first step is creating a database with two tables where each client can have multiple addresses and phone numbers.

I think its safe to assume here that I am dealing with a one to many relationship. But how should I design the tables and fields so they can store multiple addresses and phone numbers per user? By multiple I also mean indeterminate since so I can’t just have x no of columns in my table. Off Hand, here is what I was thinking:

Clients
- Id
- Notes

CONTACTS
- id
- client_id
- address
- phone number

Now I am trying to avoid a third join table like this:

Clients_Contacts
- id
- client_id
- contact id

because I still want a one to many and not many to many relationship between contacts and clients. Is there something wrong with the way I am thinking about this? Can someone please help me design this database and show me what a sample query querying multiple addresses would look like.

Answer 1

Why would you nead a join table?

I would have

Client
- ID (PK, FK of Contact)
- Notes

Contact
- ID (PK)
- client_id
- address
- phone_number

Then just set the ID of the client to be the value of client_id within the contact information.

This way, multiple Contact records can have the same client_id.