Running total for a single point in time
Hi all, In my database, I have a table with Sites, Site Operations, and Site Operation Log. A Site can have multiple Operations and an Operation can have multiple Log events. For each Operation, there is a livestock Type and Phase. I populate the Operation Log table with a starting herd size (e.g., 1000) and Phase (e.g., Nursery) and then each time the herd size changes, I add another record to the Operation Log and detail the change in herd size. What I'm interested in doing is keeping a running total of herd size through time, which I was considering calling 'CurrentTotal'. I attempted to solve this problem with a self-join with a 'Sum' function, but the 'CurrentTotal' only shows the total at this very moment, not the total as it changed with each new record in the Operation Log. How I can do this as a calculation in my table?
Thanks for your attention.