It’s week 3! From Monday to Wednesday, we worked through calculations and functions, Intro to Power BI and Data Models & Data Source Connections.
The main thing I took from our day working through data models was how helpful it can be to draw a model or parts of a model out before attempting to create it in Tableau or Power BI.
Starting with a dataset in Excel we worked through 2 questions to get us thinking of the tables and the connections needed. Following this, as a group, we came up with questions we would want to interrogate the data with.
Next it was time to draw up the models we would need to answer those questions. I used draw.io which a previous colleague loved, and found it a very nice tool for this task. It’s nicely designed with tables and other easily editable elements to add (very similar to Excalidraw). I liked the fact the tables came with several text boxes that I could edit, and I was mainly using the text boxes to input my key in each table.
Here is an example of how I was drawing out the data model needed to answer 1 of our questions:
Following this, as a group with Robbin sketching, we designed the 1 data model that could give us the answers to all questions based on the activity we had just done.
Next we recreated that exact model in Tableau and then Power BI:
I used Power BI in my previous role but for visualisation, in the sense that the BI Team created certified datasets that I could connect to and then create reports. So, building a data model from scratch was a newer experience for me.
I preferred building the model in Tableau as I found the concepts of joins and relationships slightly more straightforward in it. Although I am familiar with data models, and understanding them, in Power BI; whilst building one myself I kept running into issues. These were quickly resolved when I returned to Power Query and further cleaned the data (note: always double check for empty rows!), but I think Tableau just has more of an element of hand holding and step by step to it which really helped as a beginner.