SyteLine – Join IDO Table on Fixed Value

I am always confused of the syntax to use when customizing SyteLine. Sometimes Infor is close to a T-SQL syntax and sometimes more to the Mangoose framework syntax.
Today I tried to join a new table to an IDO. In this case, I needed to join the table on a fixed value key for my IDO. Now, when adding a new table it might be confusing, but you can actually type any join you want into the Join Text field. The example below depicts my case:

As you can see, I have used the SyteLine default reason table for joining. Now, to eliminate possible dublicates, you need to fix the reason_class  when joining. The syntax seems to be T-SQL. I am not sure, if you can write sophisticated stuff in here, but I am quite sure it is possible.