# ETL transformation validation using great expectation

**URL:** <https://discourse.greatexpectations.io/t/etl-transformation-validation-using-great-expectation/1147>\
**Category:** Archive\
**Tags:** how-to, help-wanted, types-of-expectation, expectation-request\
**Created:** [November 30, 2022, 6:59am UTC](https://discourse.greatexpectations.io/t/etl-transformation-validation-using-great-expectation/1147 "2022-11-30T06:59:32Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![sd6974](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@sd6974](https://discourse.greatexpectations.io/u/sd6974)\
**Post date:** [November 30, 2022, 6:59am UTC](https://discourse.greatexpectations.io/t/etl-transformation-validation-using-great-expectation/1147/1 "2022-11-30T06:59:32Z")

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Suppose i have a source table and has two columns first name and last name.By applying ETL logic some transformation happens and in the target table it is inserted as “First name Last name” in name column in target table.

Is it possible in great expectations to handle such kind of transformation logic with custom expectations or any way around.

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**Author:** ![Rudranil](https://avatars.discourse-cdn.com/v4/letter/r/ed8c4c/32.png) [@Rudranil](https://discourse.greatexpectations.io/u/Rudranil)\
**Post date:** [December 6, 2022, 5:32pm UTC](https://discourse.greatexpectations.io/t/etl-transformation-validation-using-great-expectation/1147/2 "2022-12-06T17:32:58Z")

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Sure, it can be easily done by a custom expectation, you need to use the columnMapexpectation class for this one.  
On a high level, Great Expectations renders the filter conditions to be sent to sqlalchemy , think of your condition as a sa.filter clause here. You can put any sql logic you want, and ge will pass that to backend sql alchemy as a filter.

Hope it helps !