Table Calculations: What are they? Let’s talk about their value first. Read this article to understand the power that they provide you.
You see this and you say, “Wow, this is incredible” and then you start using this and before your euphoria wears off, you see this article and you say “What??? What is a partition, what is addressing, and why do I care?
Long story short, you can do some amazing things with a simple click but then that one simple click can make things pretty confusing later on if you don’t know what you are doing.
Beyond the fact that this can get confusing (not too much, you just need to give it time), it can become a performance issue. Why? Read on
So, when you use a Table Calculation, what you are basically doing is a calculation on top of the data retrieved from your data source and is being currently in your visualization. Let’s take an example, let’s say you got data for your Sales down to the day level in your data source and you build a viz that looks like this
So, you now have Sales for each month, qtr and year. Great.
But, what if you want to do is to calculate the growth for each month for each year. That would mean that you want the % Diff between Jan 2014 and Jan 2013. That’s when Table Calcs come in because Tableau can use the data that is in your Viz and give you another calculation on top of that.
This could be % Growth of Q2 over Q1 within the same year OR % Growth of Q2 for 2014 when compared to Q2 sales for 2013. The possibilities are endless and so if the potential for confusion (right?) and so is the potential for creating performance issues when you try to take very granular data and then run these potentially complex calculations on top.
I, personally, have a LOVE-HATE relationship with Table Calcs (and LOD Calcs too). So, I often remind myself that I need to reduce the times I use them and use them when they really make sense.