From the course: Implementing a Data Warehouse with Microsoft SQL Server 2012

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Extracting modified data

Extracting modified data - SQL Server Tutorial

From the course: Implementing a Data Warehouse with Microsoft SQL Server 2012

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Extracting modified data

In this section, I'd like to talk about extracting modified data. When we extract data from a data source we sometime want all of the records. But it's more common that we only want the records that have been modified, since the last time we did an extraction. I'm going to talk about three different techniques of how we can determine which records have been changed recently. The first and most common technique, is just to add a date time column to every table, and use that date time column to track when was the last time this record was changed. You can do that using triggers or stored procedures to make sure you have accurate information in that last update column. Your ETL process could then simply compare the value in the date time column, to the time that you last ran the extraction and anything that's greater than, would be a record that's been modified since the last extraction. The second technique is to use change data capture, which is a function of Microsoft Sequel Server…

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