Knarr uses CData (https://cdata.com) drivers to connect with your data, which gives you a seamless and consistent experience when trying to extract and transform data from any source that we support. Whether you're pulling data from a service like MailChimp, Google Sheets, or Snowflake, you can use the same SQL syntax for each one.
If you're not familiar with SQL, W3 Schools is a fantastic free resource that you can use to learn about it. Their intro to SQL starts here: https://www.w3schools.com/sql/sql_intro.asp
For example, say you have a Google Sheet that you'd like to connect to and use to pull data into Knarr, but you don't want to pull in every field and you want to do some ETL on that data without changing the source file. No problem!
Simply connect to the sheet, click on the [SQL ->] button next to your sheet in the Tables view, and Knarr will auto-populate the SQL window with code you can easily change.
In the example below, we can see that the ID1 field is commented out, the NOC field has been aliased to Country Name, we grabbed only the first letter in the Medal field, and we limited the dataset to remove the value "NA" from the Medal field.
PS - Joins work too, so you can join together different sheets within CSVs, Excel Files, or Google Sheets. If you want to get really crazy, you can even join across different documents.