When displaying the result from database, sometime we want to do something before we display the data. For example, you don’t want to display the question of pregnancy test result for a patient whom is male in the report.
There are many ways to do that. One way I have done is to create a Variables within the Dataset. I can then refer to the same Variable in other Variables. One important aspect for Variable is that the order. You want to define the variable Prior to use it just as any programmer language.