OLAP business databases & dashboards
13 important questions on OLAP business databases & dashboards
What are the different frequencies of ETL?
Transformation can happen every day
Loading can happen every week
What are the four transformation activities?
- transfer: getting data from one system to another and for this you need things like middleware and software which interconnects applications.
- cleaning: removing noise
- integration: getting data from different databases and putting in one unified format
- aggregation: in the back-end system we might have information stored per hour, and in the database we are more interested in how the management sees things and we need to integrate things on a daily or weekly level.
What are the advantages/disadvantages of an incremental load?
Disadvantages: relatively complex to program, will take some time to work
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What are the three BI front-end applications?
- Query & reporting; static reports generated with SQL or SQL-generators via a meta layer
- OLAP; enables users to interactively analyze multidimensional data from multiple perspectives
- Data mining models; objective is to discover new valuable knowledge in databases
What is multi dimensional data?
- Data is classified into measures and dimensions
- Measures
- Summable information concerning a business process
- eg. profit, costs
- Dimensions
- Represent different perspectives on viewing measures
- Are organized hierarchically
- Hierarchy represents different levels of aggregation
- e.g. Time: month, quarter, year, all times
- Aggregating measures up to a certain dimension create a multidimensional view on the data (= data cube)
What are the OLAP operators?
- Roll-up
- Drill-down
- Slice & Dice
- Pivot or Rotate
How many cubes (i.e. Aggregations) are there in a multi-dimensional database with n dimensions?
- No dimension hierarchies: 2n
- With hierarchies
What is a snowflake schema?
Why a snowflake schema instead of a star schema?
However, you lose the advantages of the star schema. It is not easily understood by end-users, high number of joints and no predictable/standard framework
Why use surrogate keys?
What are the three solutions by Kimball for slowly changing dimensions?
- Overwrite old value = restating (infrequent changes (e.g., new customer address))
- Add 'version number' field as part of the key (Small individual changes( e.g., store size has been enlarged))
- Add new column(s) to dimension table (Suddenly big changes (e.g., new categorization))
What are business dashboards used for?
What are the 3 layers with design dashboard situation awareness?
- Capability of the management of being aware of what is happening around the company (perception of the elements in the environment)
- Understanding what that information means for the company now (comprehension of the current situation)
- Future (a projection of future status)
The question on the page originate from the summary of the following study material:
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- Never study anything twice again
- Get the grades you hope for
- 100% sure, 100% understanding
