Normalization and record deletion

[bob von ilten]

I am trying to understand the "Normalizing" process and how it should be applied to database design. I have a db (mysql5) with several tables. Four of them being clients, addresses, room, invoices. they are broken up this way because a client can have many addresses and addresses can have many rooms, and hopefully a client will have many invoices/workorders. My question is this. After normalizing the client, addresses, and rooms tables the creation of an invoice pulls from three different tables, so would the invoice table hold all data related to a particular invoice or would it just hold the data that was not stored in any of the other tables. If it did only store the data not stored by the other tables how would you preserve the integrity and history of the invoice table upon the deletion of a client record?

TIA