Discussion1: What does mandatory/required variable in a query mean?

Topic: What does mandatory or required variable in a query mean?

QA: It means user has to input something for this variable. If no input, user could not go to next, or the Run/Next button is supposed to display disabled.

Developer: No, it should allow user either input or no input. If input any value, the value will be used. If no any value input, null will be used. Query will be run with it as empty value or no value.

QA: What is it different from Optional field for user?

Developer: Optional field will be skipped in the logic layer if it is empty. That is totallyl different with mandatory with null. It means logic layer always uses it as a query condition.

Note: This might not be a typical example to address the different mindset between QA and developer. But it tells me something of the reason why user and development could not be in the same line without communicating. I'd like to collect as many as this tiny disscussion, to helps extend my mind.