How to display the prompt value in PS-Query results?

If we would want to display the prompt value in PS-Query then, mostly we would add the corresponding field to the query results instead of the prompt value.
For example the query is written as:
A.EFFDT <= :1
If we want to display the value entered by user, until now we would have used A.EFFDT to the query results since the prompt -:1 cannot be selected in query results.



What if we had some sort of calculation on a value entered by user in the prompt?
Something like:
A.EFFDT <= (:1-30)
(:1 - 30) - can be added to a PS-Query expression and the query could perform the desired result. So, in this case how do we know the value entered by the user? 
Simple.

1. The prompt should be used within an an expression if it should be displayed in the query results. This is already done above.
2. Select this expression to the fields list in the query results.
3. Now, on the Aggregate tab of this field(Prompt - expression in fields list) chose either Min or Max. If this step is not performed it would result in a SQL error.