@FediMannoubi Below is a basic approach to solve. Assuming both postgres tables are populated with rows per your example, your nifi flow would need to get the CSV (various ways to do that), once the contents of the csv are in a flowfile (i use GenerateFlowFile processor), you can use a RecordReader based processor to read the csv. This will allow you to write SQL against the flowfile with QueryRecord to get a single value. For example: SELECT city_name FROM FLOWFILE Next, in your flow you will need to get the city_name value into an attribute, i use EvaluateJsonPath. After that a ExecuteSQL processor and associated DBCP Connection pool to postgres. Then in ExecuteSQL your query is SELECT city_id FROM CITY WHERE city_name=${city_name} At the end of this flow you will have the city_name from csv, and city_id from postgres. You can now combine or use the further downstream to suit your needs. INSERT is done similarly, once you have the data in flowfiles, or attributes, using the same ExecuteSQL you write an insert instead. My test flow looks like this, but forgive the end, as I did not actually have a postgres database setup. You can find this sample flow [here]. I hope this gets you pointed in the right direction for reading csv and querying data from database.
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