a2zinterviews

13.	What do you mean by fact table?
	A fact table is the central table that contains the measures or facts of a business process.
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14.	What do you mean by data mart?
	A data mart can contain one fact table to address one subject. In such a case,when a number of data marts are integrated to create a data warehouse, it is important that the facts in each table mean the same thing. Such facts (i.e., measures or metrics) that have the same meaning in different data marts are called conformed facts.
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15.	What do you mean by data staging?
	Data staging is the process of transferring the data from the data sources (operational systems) into the target database of the data warehouse. The ETL process can be divided into the following stages: Extraction of data from various data sources Cleansing of data which includes trying to ensure that important data is not missing, field names are changed appropriately for good readability, etc. Transformation of the source data in a form suitable for data warehouse, (see below for various transformations) Loading of data into the target database Quality Assurance of data which is done at every stage of ETL to ensure that the data that is going into the data warehouse is accurate, consistent and reliable. This is also known as data scrubbing.
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16.	What are the different types of scd?
	Type 1 SCD: In the dimension table, the new data replaces the old data. In other words, the historical data is not preserved. Type 2 SCD: New records are added to the dimension table. The old record containing the old data is retained and the new record contains the new data. Type 3 SCD: New fields are added to the dimension table so that the table can hold both old values and new values in the same record.
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