Sometimes we want to build a waterfall chart to compare the margin between last year (hereinafter referred to as “LY”) and this year (hereinafter referred to as “TY”).  i.e. Current period (2020/10 which is selected by slicer) = 57% and prior period (2019/10) = 50%, the Diff will be 7%. To show the changes between LY and TY, we need to add LY and TY in Category Field, and add Diff in Breakdown Field. However, in our data model, it usually does not contain LY, TY and Diff directly. We need to create a category table and a breakdown table to help us build this waterfall chart.