Sometimes you find yourself dealing with a fact table consisting of an event with an effective start date and an effective end date. Some typical examples of these cases are employee absences (an absence has a start date and end date), salaries (a salary has a period when it was effective) or item in a warehouse (date in and date out of the item).
In these situations, the following reporting need can arise: “how many employees were on leave in Aug 15th?”, “what was the salary of employee X last month?”, “how many units of item IT1 were there in warehouse W2 in Nov 30th?”.
