https://docs.confluent.io/5.4.1/ksql/docs/developer-guide/syntax-reference.html#struct-overview Confluent docs say they don't accept Properties as a valid field name, but why?
What if I do have a schema with Properties, what can I do then?
It's a keyword/reserved word in the language. I'm not familiar with ksql specifically, but most sql distributions provide backticks to escape references for this reason (and more). Without those, it'd make sense you couldn't use it.
As an example of using backticks in a pretty standard sql statement:
SELECT `table`.`properties` FROM `table` ...