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Editorial Team
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Asked: 2026-06-17T10:05:15+00:00

I have been asked at many interviews the same question again and again.The question

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I have been asked at many interviews the same question again and again.The question is how would you test incremental data which gets loaded every day in their database.My position is Data warehouse QA plus BA.The main purpose of testing is to check if we have all the data from source and then to test if all the data copied from source got placed in respective tables as designed by developers.

So every time somebody asks this question i answer like this:To test incremental data we take data from staging tables which will have the data for the daily incremental file.So now i can compare the staging table against the target database.Like all databases there might be some calculation or joins we did according to design to get data from staging to production so i will use that design to make my queries to test data in production against source.

So my question here is i have tested incremental loads this way in the only project i did so can anybody give me detailed answer because i think i might not be answering it right.

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1 Answer

  1. Editorial Team

    Incremental loads are inevitable in any data warehousing environment. Following are the ways to render the incremental data and test it.

    1) Source & Target tables should be designed in such a way where you should store date and timestamp of the data (row). Based on the date and timestamp column(s) you can easily fetch the incremental data.

    2) If you use sophisticated ETL tools like informatica or Abinitio, then it is simple to see the status of the loads chronologically. These tools store the information for every load. However it has some limitation to store the last 10 loads. You need to configure it to store for more than 10 loads.

    3) If you are not using sophisticated ETL tools then you should build ETL strategies to store the statistics of the load and capture the information (like no. of inserts, deletes, updates etc.,) during the load. These information can be retrieved whenever you need. But it needs lots of technical knowledge to adopt.

    If you want to succeed in a data warehouse interview, i would suggest the best iOS application(data-iq) created by a us based company and its for candidates like you . check it out and you may like it. good luck for your interview.

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