ESQL to compare data in two indexes based on a unique key

Elastic Stack Kibana
1

Hi Team,

I am having two indexes in elasticsearch/kibana and wanted to write a ESQL query which will fetch the documents based on a unique field where the documents are there in index1 but not in index2. Could you please let me know if we can achieve this using ESQL.

For easy understanding SQL format:

SELECT unique_key
FROM "index1"
WHERE unique_key NOT IN (
    SELECT unique_key 
    FROM "unique_key"
)