The Java EE 5 Tutorial

Tables Representing Business Entities

Figure 37–2 shows the relationships between the database tables. The bank_customer and bank_account tables have a many-to-many relationship: A customer can have several bank accounts, and each account can be owned by more than one customer. This many-to-many relationship is implemented by the cross–reference table named bank_customer_account_xref. The tables named bank_account and bank_tx have a one-to-many relationship: A bank account can have many transactions, but each transaction refers to a single account.

Figure 37–2 Database Tables

A diagram showing the bank_customer, bank_account, bank_tx,
and bank_customer_account_xref database tables and their relationships.

Figure 37–2 uses several abbreviations. PK stands for primary key, the value that uniquely identifies a row in a table. FK is an abbreviation for foreign key, which is the primary key of the related table. Tx is short for transaction, such as a deposit or withdrawal.