MySQL数据库中的循环引用

Question

I am working on a database where I have a customer table, a vendor table and an address table. I thought I'd put a customer id and vendor id in each row of the address table, but allow them to be null.

A vendor will likely have one address at a time, but just in case, I'll create it to allow multiple addresses.

A customer will often have 2 addresses, but might have many.

The customer table will have the fields "default_shipping_id" and "default_billing_id"

I can do this without the FOREIGN KEY constraint, but if I try to create these tables with the constraints, I get errors because of the circular reference. Should I make the constraint one-way or can/should I add the constraints after the tables have all been created?

Answer 1

Try to be neat and flexible with designing databases. 5 tables for your solutions -

1) `address` table
`id`
`address`

2) `customers` table
`id`
`name`
`email`

3) `customer_address_mapping` table
`id`
`customer_id` (FK to `customers` table)
`address_id` (FK to `address` table)
`is_billing` (Boolean field)
`is_shipping` (Boolean field)

4) `vendors` table
`id`
`name`
`email`

5) `vendor_address_mapping` table
`id`
`vendor_id` (FK to `vendors` table)
`address_id` (FK to `address` table)

Explanation:

address table will be a dump of all the addresses of all customers and vendors . Both mapping tables will provide you flexibility to add as many addresses you want. is_billing and is_shipping boolean fields will let you know the type of address of the customer.