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A dimensional modeling matrix is used to define the relationship between the dimensions and facts. A data warehouse expands as the data marts added to it in a sequential manner (i.e. one at a time). Data mart is also known as fact and their dimensions. A simple data dimensional modeling example for a college is defined as below.
Fig 10.2: Dimensional Modeling Matrix
ETL is combined of three processes, i.e. Extract, Transform and Load. These are the three essential steps to pull data out from a source (may be a database, data warehouse or some other source) and place it into a database or data warehouse. The ETL process is defined below.
Extract: It is the process of reading the data from source. The source can be a database or something else which provide data that can be inserted into the database or data warehouse.
Transform: It is the process of converting data obtained previously so that it can be placed into our database. When we have data from outer source, we cannot directly insert it into database. It needs to be transformed. Let’s take a simple example of ECG (electrocardiogram). The output of ECG is sinusoidal waves which cannot be inserted into database. But we can still save them into our database by converting them into the format which can be understandable by database.
Load: The process of writing data into database is known as load.
The ETL processes are majorly used in case of data migration.
