If I understood your question correctly, you don't actually need to bring the data in three times. You can use LOD expressions in Tableau to display results in multiple levels of detail or in a level of detail different from the current view.
I understand you are working with hospital data and so may not be able to post any dataset on the forum. Let me know if you require further clarifications or if you can mockup an example using any sample dummy dataset.
Hope this helps.
Thank you so much It occured to me when I went to get a coffee that LOD might be the answer but I didn't have it clear enough in my head to work it out. Your answer is perfect!