How to End a Query if Condition is Met (Query Editor / M)

Hi all,

I am looking for a solution that says:

if <condition> then <perform action> else <end query> 

Is this possible in M?

Also there are a number of queries where if a condition is met, I effectively don't want the query to execute at all. Is that possible?  For example:

if <Parameter A = "Disable"> then  <end query without any content> else <query actions>

Cheers

Kirsty