ans should be D
Datawarehouses are huge. If a department has its own data mart, it can customize the data as the data flows into the data mart from the data warehouse. It can summarize,sort,select and structure its own data.
Data mart vs data warehouse
- Holds multiple subject areas
- Holds very detailed information
- Works to integrate all data sources
- Does not necessarily use a dimensional model but feeds dimensional models.
- Often holds only one subject area- for example, Finance, or Sales
- May hold more summarized data (although many hold full detail)
- Concentrates on integrating information from a given subject area or set of source systems
- Is built focused on a dimensional model using a star schema.