Question

In my application I have a Customer class and an Address class. The Customer class has three instances of the Address class: customerAddress, deliveryAddress, invoiceAddress.

Whats the best way to reflect this structure in a database?

• The straightforward way would be a customer table and a separate address table.
• A more denormalized way would be just a customer table with columns for every address (Example for ‘street’: customer_street, delivery_street, invoice_street)

What are your experiences with that? Are there any advantages and disadvantages of these approaches?

Answer 1

If you are 100% certain that a customer will only ever have the 3 addresses you described then this is OK:

CREATE TABLE Customer (     ID int not null IDENTITY(1,1) PRIMARY KEY,     Name varchar(60) not null,     customerAddress int not null         CONSTRAINT FK_Address1_AddressID FOREIGN KEY References Address(ID),     deliveryAddress int null             CONSTRAINT FK_Address2_AddressID FOREIGN KEY References Address(ID),     invoiceAddress int null             CONSTRAINT FK_Address3_AddressID FOREIGN KEY References Address(ID),     -- etc )  CREATE TABLE Address (     ID int not null IDENTITY(1,1) PRIMARY KEY,     Street varchar(120) not null     -- etc ) 

Otherwise I would model like this:

CREATE TABLE Customer (     ID int not null IDENTITY(1,1) PRIMARY KEY,     Name varchar(60) not null     -- etc )  CREATE TABLE Address (     ID int not null IDENTITY(1,1) PRIMARY KEY,     CustomerID int not null         CONSTRAINT FK_Customer_CustomerID FOREIGN KEY References Customer(ID),     Street varchar(120) not null,     AddressType int not null      -- etc )