Assignment: Based on Book Retail Sales
See Reading Guide provided below, after the questions. The assignment tests only a very small share of the content of the chapter. If you are pressed for time and end up skipping some parts of the chapter, do make sure to read them later.
Please note that your responses should ideally not be verbatim reproduction of book content. Read, think about what you read, and write down your own representation of the key ideas relevant to each response. This will impact grading.
1. What is ‘atomic' data? In the context of POS sales, what is the most atomic data? What are the advantages of choosing the grain to be the most atomic?
If we choose grain as each POS transaction (that is, each fact table row corresponds to one transaction at the cash register), what would be an example of a query we cannot answer, and one we can answer, with the new star schema?
A query we cannot answer := choose an example query that we can answer with the grain selected in the book chapter, but can no longer be answered once we change the grain as described above.
2. In RDBMS, Holiday will be stored as Y/N (or 1/0), to conserve space and be more efficient. Why does a DW choose a different approach? (DW- Data Warehouse). What fundamental principle of DW is emphasized here?
3. Give some reasons why a DW would use a Date dimension. (instead of doing things like an operational database which would store date as an attribute)
4. List some advantages of using surrogate keys in a dimension table.
5. Promotion dimension describes factors that may cause changes in product sales, the fact being measured. For this reason, Promotion is called a ______ dimension. ( looking for a single word response).