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

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12.7. CHAPTER SUMMARY

  • ETL functions in a data warehouse are most important, challenging, time-consuming, and labor-intensive.

  • Data extraction is complex because of the disparate source systems; data transformation is difficult because of the wide range of tasks; data loading is challenging because of the volume of data.

  • Several data extraction techniques are available, each with its advantages and disadvantages. Choose the right technique based on the conditions in your environment.

  • The data transformation function encompasses data conversion, cleansing, consolidation, and integration. Implement the transformation function using a combination of specialized tools and in-house developed software.

  • The data loading function relates to the initial load, regular periodic incremental loads, and full refreshes from time to time. Four methods to apply data are: load, append, destructive merge, and constructive merge.

  • Tools for ETL functions fall into three broad functional categories: data transformation engines, data capture through replication, and code generators

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