Designing Satellite tables
Hubs and Links only contain keys. Hubs only contain the business keys of entities, not descriptive data of those entities. Links only contain foreign keys to Hubs or other Links, but again, no descriptive data. We do create the LoadDate and Source columns, but these are not real descriptive data of the entities or the relationships. We add Satellite tables to the main structure of the Data Vault as defined by the Hubs and the Links. Satellite tables, or just Satellites, contain the "real" data, the descriptive data. This, of course, includes non-unique data values such as product color.
A Satellite is a table containing detailed and historical descriptive data columns of a Hub or a Link. Figure 9.8 shows a Satellite:
Figure 9.8 – Satellite table
A Satellite has the following columns:
- The hash key of the Hub or Link it belongs to
- The load date of the row
- The end date of the row
- The actual descriptive...
