Designing Hub tables
As already mentioned, Data Vault distinguishes between three different types of tables: Hub tables, Link tables, and Satellite tables. The first step in the modeling process is to find the Hub tables, or just Hubs. Hubs have a direct relationship to what we called entities in Chapter 2, Entity Analysis. Data Vault calls these business keys. Each entity has a characteristic that makes it unique. That characteristic was called a logical key in Chapter 1, Introduction to Databases. In Data Vault, it is called the business key. Each business key (that is, each entity) will be implemented as a Hub table. A sales process will have a Hub for products and a Hub for customers. Product and Customer are the entities involved in a sales transaction.
A Hub table has only four columns. You can see a Hub table example in Figure 9.4:
Figure 9.4 – Hub table
All the columns in the Hub table are mandatory and you should always create them in order...
