Support of SELECT EXISTS (subquery) in preConditions

I want to write a preCondition with an sqlCheck and the SQL looks like SELECT EXISTS (subquery)
This returns a boolean from the database, but I can’t figure out what expectedResult=“???” should be. I’ve tried “1” or “0”, “t” or “f”, “true” or “false” against a PostgreSQL instance but that didn’t help. So, is it possible to do something like this?

Can you just convert the query to a count(*) so it returns an integer? Might be easier.

Hello, thank you for chiming in. I am aware of COUNT(*) but for many reasons like performance many of times the correct thing to do is EXISTS.