This article will help fixing the issue when a query using the external table and a database table using the IN clause
Environment
Vertica Version 25.2 and higher
Situation
A query when using the IN clause as below:
select distinct fact_test_ext.coln as coln from <schema>.fact_test_ext
where coln in (select distinct coln from <schema>.factOtherTable);
did not return the expected result..