DAX is a tricky language; on the surface it is deceptively simple, but under the hood it can quickly become complex and it can take many years to master. If you have ever typed a formula and crossed your fingers when you press Enter, then you know what I mean. If you are reading this article, you are no doubt already on your own DAX learning journey.
As you become more competent at DAX, you will start to write more complex formulas that behave differently depending on the filters in your visuals. One such example is the P&L report that I shared in 2020. This report contains quite a tricky formula. It was built slowly and methodically, one step at a time, until it was working as desired. This is the best way to write DAX. If you want to see how I do it, then go back to the article linked above and watch the video. While I recommend this as the best approach to writing formulas, the reality is that sometimes you will need to go back to a formula you wrote previously and debug that formula. Maybe it is not working correctly, or maybe you need to enhance it for some reason. Whatever the reason, today I am sharing with you my technique to debug complex formulas using tool tips.
Read the whole thing.