Hi Pranaya D,
You can directly pass the Drop down values to the OQl query, or you can also create Variables for all drop down and set the Values and then pass the variables to OQL Query.
The market value you have highlighted as empty might be because you have not selected the Drop down value.
Check the below SS this might help you :
I am selecting year via Drop down and printing that value in Create Variable.
So I think like you are trying to filter depending upon drop downs
The Best Practice is you keep (*-*) Association between both the entities
Later on the reference selector write an On click action
Case 1 :Create a List (of the data which you want)→ Check decision for empty → If empty then retrieve the entire data → change list ( add retrieved list in created list which you added in the beginning → change object (call that *-* association in that object , later pass the initial created list )
Case 2: Create a String (Inside that string call that *-* association)Create a List (of the data which you want)→ Check decision for empty → If not empty then retrieve the entire data which matches the initial string→ change list ( add retrieved list in created list which you added in the beginning → change object (call that *-* association in that object , later pass the initial created list )