Data Warehousing Fundamentals for IT Professionals

CHAPTER 12

DATA EXTRACTION, TRANSFORMATION, AND LOADING

CHAPTER OBJECTIVES

• Survey broadly all the various aspects of the data extraction, transformation, and loading (ETL) functions
• Examine the data extraction function, its challenges, its techniques, and learn how to evaluate and apply the techniques
• Discuss the wide range of tasks and types of the data transformation function
• Understand the meaning of data integration and consolidation
• Perceive the importance of the data load function and probe the major methods for applying data to the warehouse
• Gain a true insight into why ETL is crucial, time consuming, and arduous

You may be convinced that the data in your organization's operational systems is totally inadequate for providing information for strategic decision making. As information technology professionals, we are fully aware of the futile attempts in the past decades to provide strategic information from operational systems. These attempts did not work. Data warehousing had begun to fulfill that pressing need for strategic information.

Mostly, the information contained in a warehouse flows from the same operational systems that could not be directly used to provide strategic information. What constitutes the difference between the data in the source operational systems and the information in the data warehouse? It is the set of functions that fall under the broad group of data extraction, transformation, and loading (ETL).

ETL functions reshape the relevant data from ...