MC	Which of the following is not a characteristic of a data warehouse?	Subject-oriented	incorrect	Time-variant	incorrect	Integrated	incorrect	Volatile	correct	
MC	Which statement is NOT CORRECT?	A charecteristic of data warehouses is that they are integrated.	incorrect	To speed up report generation and avoid time consuming joins in a star schema, the dimension tables need to be normalized.	correct	OLAP allows you to interactively analyze the data, summarize it, and visualize it in various ways	incorrect	Operational data is always up-to-date and represents the most recent state.	incorrect	
MC	Which statement is CORRECT?	A data lake is less agile compared to a data warehouse which has no structure.	incorrect	In case of a data warehouse, the data schema definitions are only determined when the data is read (schema-on-read) whereas for data lakes it is fixed when the data is loaded (schema-on-write).	incorrect	A key distinguishing property of a data lake is that it stores raw data in its native format which could be structured, unstructured or semi-structured.	correct	A data lake is targeted towards decision makers at middle and top management level, whereas a data warehouse requires a data scientist, which is a more specialized profile in terms of data handling and analysis.	incorrect	
MC	Which statement is CORRECT?	In case of a data warehouse, the data schema definitions are only determined when the data is read (schema-on-read) whereas for data lakes it is fixed when the data is loaded (schema-on-write).	incorrect	A data warehouse is a scaled-down version of a data mart aimed at meeting the information needs of a homogeneous small group of end-users such as a department or business unit. 	incorrect	A junk dimension can be used for attribute types that are highly correlated, high in cardinality and simultaneously updated.	incorrect	The extraction strategy of ETL can be either full or incremental.  In the latter case, only the changes since the previous extraction are considered.	correct	
MC	Which statement is CORRECT?	To speed up report generation and avoid time consuming joins in a star schema, the dimension tables need to be normalized.	incorrect	The dimension tables of a star schema contain the criteria for aggregating the measurement data and will typically be used as constraints to answer queries.	correct	A star schema has one large central dimension table which is connected to various smaller fact tables.	incorrect	The dimension tables in a star schema are frequently updated.	incorrect	
MC	Which statement is NOT CORRECT?	The key fundament of OLAP is a multidimensional data model which can be implemented in various ways.	incorrect	A pivot or cross-table is a popular data summarization tool.  It essentially cross-tabulates a set of dimensions.	incorrect	Query and reporting tools are an essential component of a comprehensive business intelligence solution.	incorrect	A key disadvantage of OLAP is that it does not allow to interactively analyze your data, summarize it and visualize it in various ways.	correct	
MC	Which statement is NOT CORRECT?	At the operational level, day to day business decisions are made, typically in real-time or with a short time frame.	incorrect	A virtual data warehouse (sometimes also called a federated database) or virtual data mart contains no physical data but provides a uniform and consolidated single point of access to a set of underlying physical data stores.	incorrect	At the strategic level, decisions are made by senior management with long term implications (e.g., 1, 2, 5 years or more)	incorrect	In a data warehouse context, an outrigger table can be defined to store a set of attribute types of a dimension table which are not correlated, high in cardinality and updated sequentially.	correct	
MC	Which statement is CORRECT?	Roll-up (or drill-up) refers to aggregating the current set of fact values within or across one or more dimensions.	incorrect	Roll-down (or drill-down) de-aggregates the data by navigating from a lower level of detail to a higher level of detail.	incorrect	Slicing represents the operation whereby one of the dimensions is set at a particular value.	incorrect	Dicing corresponds to a range selection on one or more dimensions.	incorrect	All statements are correct	correct	
MC	Which statement is NOT CORRECT?	Relational OLAP (ROLAP) stores the data in a relational data warehouse, which can be implemented using a star, snowflake or fact constellation schema.	incorrect	MOLAP scales better to more dimensions than ROLAP.  The query performance may however be inferior to ROLAP unless some of the queries are materialized or high-performance indexes are defined.	correct	Multidimensional OLAP (MOLAP) stores the multidimensional data using a Multidimensional DBMS (MDBMS) whereby the data is stored in a multi-dimensional array-based data structure optimized for efficient storage and quick access.	incorrect	Hybrid OLAP (HOLAP) tries to combine the best of both MOLAP and ROLAP.  An RDBMS can then be used to store the detailed data in a relational data warehouse whereas the pre-computed aggregated data can be kept as a multidimensional array managed by a MDBMS.	incorrect	
MC	In terms of data manipulation, a data warehouse focusses on...	Delete statements	incorrect	Select/Update statements	incorrect	Insert/Update/Delete/Select statements	incorrect	Insert/Select statements	correct