What is ETL? A Quick & Easy Example!

If you have heard the acronym ETL and wondered what it is? then you are in the right place!

ETL is an acronym for Extract, Transform & Load, but this won’t explain anything.

Instead of giving you the textbook definition, let me explain it to you with an example.

Assume that you are the owner of 10 different retail stores and you would like to see key metrics from all of the stores every day like stocks, profits, no of sales, etc. in one report. To make it more interesting let us assume that each store manages data in its own separate database that may use different technologies.

So now, how to get the data you want from all of these different stores? So one way to do it is by creating another database that has data from all the different store’s databases. Here, in this case, you use the ETL approach to integrate the data.

Extract

Now either your programmers can write a piece of code or use some ETL tool to connect all the different databases and pull the required information from all of them, this is the process of extraction.

Transform

After extracting the data, we have to ensure that all the data is in the same format. For example, if one store is using dd/mm/yyyy date format and another store is using mm/dd/yyyy format then you have to standardize them to be in one format in the final combined database and this is simply the process of transformation.

There are many data anomalies you might come across while transforming the data and I have another blog discussing some of them. You can check that out if you are interested.

Load

Once the data is standardized, it has to be loaded efficiently to the final database without much delay and this is the final part of it.

It is very important that this process runs efficiently otherwise you may not see the data on time or you may see the wrong numbers in your report.

I hope this short post gave you a little bit of understanding about ETL. If you want me to go deeper into the technical aspects of it then please let me know in the comments!

Take care and meet you in the next one.

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Abhilash Marichi

Abhilash Marichi

Data Engineer at Amazon. I write about Data, Product & Life.