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DATA WAREHOUSING FUNDAMENTALS: A Comprehensive Guide for IT Professionals by Paulraj Ponniah

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12.6. ETL SUMMARY

By now you should be fully convinced that the data extraction, transformation, and loading functions for a data warehouse cover very wide ground. The conversion functions normally associated with the development of any operational system bear no comparison to the extent and complexity of the ETL functions in a data warehouse environment. The data extraction function in a data warehouse spans several, varied source systems. As a data warehouse developer, you need to carefully examine the challenges the variety of your source systems pose and find appropriate data extraction methods. We have discussed most of the common methods. Data extraction for a data warehouse is not a onetime event; it is an ongoing function carried out at very frequent intervals.

There are many types of data transformation in a data warehouse with many different tasks. It is not just a field-to-field conversion. In our discussion, we considered many common types of data transformation. The list of types we were able to consider is by no means exhaustive or complete. In your data warehouse environment, you will come across additional types of data transformation.

What about the data loads in a data warehouse in comparison with the loads for a new operational system? For the implementation of a new operational system, you convert and load the data once to get the new system started. Loading of data in a data warehouse does not cease with the initial implementation. Just like extraction and ...

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