* null values ARE NOT included in lenses,etc which may result in inaccurate row counts. Always try to bin nulls into 'unspecified'.

In certain use cases, null values need to be backfilled with stubs in order to properly group or summarize. In example below, SAQL is used to fill null values of Grades with the text 'unspecified'. 
Step 1: Create a compute expression, add field called 'backfill me'
Step 2: Choosing text type, type expression in SAQL Expression box. 
case when 'Grades__c'  is null then "UnspecGrade"
else 'Grades__c'  end