Is it possible to use variable as comment within optional brackets?


I'm trying to have variables variable as comment within optional brackets?. I have read this discussion and this pull request.

What I am trying to do here is I would like to parse UNION ALL SELECT * from step_2 when there is value in variable Step_2. Otherwise, it should only parse select * from step_1. However the value of variable Step_2 is not meaningful in my query. Therefore, I would like to comment it, making it not a functional code. Then it shows the error. Is this function supported in metabase? Or did I make any mistake?

Thank you!