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In Depth Information
All of these common issues essentially demand an area where you can happily carry out all your operations—a
staging or data-preparation platform. How would you take advantage of a staging environment? Here are the tasks
you’d perform:
1.
Identify the data sources, and prepare a data map for the existing (source) tables and entities.
2.
Copy the data sources to the staging environment, or use a similar process to achieve this.
This step essentially isolates the data from the original data source.
3.
Identify the data source tables, their formats, the column types, and so on.
4.
Prepare for common ground; that is, make sure mapping criteria are in sync with the
destination database.
5.
Remove unwanted columns.
6.
Clean column values. You definitely don’t want unwanted information—just exactly
enough to run the analysis.
7.
Prepare, plan, and schedule for reloading the data from the source and going through the
entire cycle of mapping.
8.
Once you are ready, use proper ETL tools to migrate the data to the destination.
Transformation
Let’s begin with a simple flow diagram, shown in Figure 1-8 , which shows everything put together very simply.
Think about the picture in terms of rows and columns. There are three rows (for system, language used, and purpose)
and two columns (one for OLTP and the other for OLAP).
Figure 1-8. Converting from OLTP to OLAP
 
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