DATABASE FUNDAMENTALS
DATA WAREHOUSING AND DATA MINING
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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To store data in one operational system
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To retrieve data from an operational system
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To combine data from heterogeneous sources
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To take the dimension and change its granularity
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Detailed explanation-1: -Why aggregate is used in dimensional model of data warehouse? Aggregates are used in dimensional models of the data warehouse to produce dramatic positive effects on the time it takes to query large sets of data. A more common use of aggregates is to take a dimension and change the granularity of this dimension.
Detailed explanation-2: -Aggregates are used in dimensional models of the data warehouse to produce positive effects on the time it takes to query large sets of data. At the simplest form an aggregate is a simple summary table that can be derived by performing a Group by SQL query.
Detailed explanation-3: -Aggregate data is typically found in a data warehouse, as it can provide answers to analytical questions and also dramatically reduce the time to query large sets of data. Data aggregation is often used to provide statistical analysis for groups of people and to create useful summary data for business analysis.
Detailed explanation-4: -The grain of the dimensional model is the finest level of detail that is implied when the fact and dimension tables are joined. For example, the granularity of a dimensional model that consists of the dimensions Date, Store, and Product is product sold in store by day.
Detailed explanation-5: -In data warehousing, granular data or the data grain in a fact table helps define the level of measurement of the data stored. It also determines which dimensions will be included to make up the grain. These measurements of fact describe what you have populated in each row.