Bert Wagner has more fun with math in SQL Server:
Years ago I was writing a query for a stacked bar chart in SSRS. The chart intended to show the percentage breakdown of distinct values in a table. For example, the chart would show that value A made up 30% of the rows, B made up 3%, C made up 12% and so on. Since every row had a value, I was expecting the stacked bar chart percentages to add up to 100%
However, in many instances the charts would come up short; instead of a full 100%, the percentages would only add up to 98% or 99%. What was going on?
Bert dives deeply into the topic and then gives us some practical suggestions on how to deal with it.