Subject Re: [firebird-support] Annoying: CTE "CTE2" is not used in query
Author Louis van Alphen
Thinking about it yes i agree. Ultimately, if the CTE is not used, FB need not execute the query. No CPU cycles lost. Maybe a warning in the query plan, but an error is too restricting

Unlike Louis, I don't understand why this results in an error, I'd say
Firebird is too picky in this case.