Hello Experts,May I know that what is the incremental extraction and incremental loading? And how can we do both?Kindly let me know the solution of it.Thanks in advance., What is the Incremental Extraction and Incremental Loading?, BI (Business Intelligence) Forum | STechies Hello Experts,May I know that what is the incremental extraction and incremental loading? And how can we do both?Kindly let me know the solution of it.Thanks in advance., What is the Incremental Extraction and Incremental Loading?, BI (Business Intelligence) Forum Feedback Download App
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How you do incremental extraction depends on the source system design. In fact, certain source systems do not initially provide a mechanism to target changes and new rows. In these cases, sometimes you have the flexibility to make changes on the source system, sometimes you don’t.
http://flylib.com/books/en/1.515.1.27/1/
There are two types of logical extraction methods: Full Extraction: Full extraction is used when the data needs to be extracted and loaded for the first time. In full extraction, the data from the source is extracted completely. This extraction reflects the current data available in the source system. Incremental Extraction: In incremental extraction, the changes in source data need to be tracked since the last successful extraction. Only these changes in data will be extracted and then loaded. These changes can be detected from the source data which have the last changed timestamp.
http://www.folkstalk.com/2011/04/extraction-methods-in-data-warehouse.html
One more method to get the incremental changes is to extract the complete source data and then do a difference (minus operation) between the current extraction and last extraction. This approach causes a performance issue. Physical extraction The data can be extracted physically by two methods:
http://www.folkstalk.com/2011/04/extraction-methods-in-data-warehouse.html
The current incremental identifying column value needs to be stored so that each ETL run can use a new value for the extraction. This can be done in various ways (such as keeping it in a file), but the most common way is to store the value in a database control table that contains only the extraction information.
http://flylib.com/books/en/1.515.1.27/1/
Incremental Extraction Using a Change Identifier Value If your source tables contain a change identifier value (such as a last modified datetime), or you are able to make small changes to your source tables to allow this, then the process in SSIS will involve three steps: 1  Targeting the changed records by making the source query dynamic.
http://flylib.com/books/en/1.515.1.27/1/
Incremental Data Extraction. Incremental Data Extraction. Incremental extraction is the process of targeting modified records and new records, and then tracking the last completed extraction. For example, as you process rows, you might track the last modified datetime value or last identifier for the rows that you’ve pulled.
http://flylib.com/books/en/1.515.1.27/1/
Using SSIS, a couple approaches are possible that use properties of the source adapter. 1  Using an OLE DB source adapter may allow a parameterized query, where the query can reference package variables to filter the query. 2  The OLE DB adapter also allows the source table name or query to be embedded into a package variable.
http://flylib.com/books/en/1.515.1.27/1/
Offline Extraction: The data from the source system is dumped outside of the source system into a flat file. This flat file is used to extract the data. The flat file can be created by a routine process daily.
http://www.folkstalk.com/2011/04/extraction-methods-in-data-warehouse.html
As you can see, this gives you a nice way to handle incremental extraction from a SQL source without requiring application changes or a table trigger. Yes, it does require the addition of an 8-byte column in the source, but the incremental extraction benefits may outweigh the additional table width.
http://flylib.com/books/en/1.515.1.27/1/
what is incremental extraction
Incremental extraction is the process of targeting modified records and new records, and then tracking the last completed extraction.