Dax Alternative

Hi Guys,

Data looks like this though I've annonomised the UPN-SUID column but it comprises a start date and end date. If the end date is null they are still present: 

UPN-SUID,DOA,Leaving date
12600,01-Sep-14,09-Feb-17
12601,01-Sep-14,28-Jun-19
12602,01-Sep-14,
12603,01-Sep-14,11-Dec-18
12604,01-Sep-14,31-Oct-16
12605,01-Sep-14,15-Oct-17
12606,01-Sep-14,13-Sep-18
12607,01-Sep-14,11-Dec-18
12608,01-Sep-14,17-May-19
12609,01-Sep-14,10-Sep-17
12610,01-Sep-14,28-Jun-19
12611,01-Sep-14,
12612,01-Sep-14,
12613,01-Sep-14,
12614,01-Sep-14,
12615,01-Sep-14,
12616,01-Sep-14,28-Jun-19
12617,01-Sep-14,28-Jun-19
12618,01-Sep-14,28-Jun-19
12619,01-Sep-14,28-Jun-19
12620,01-Sep-14,28-Jun-19
12621,01-Sep-14,28-Jun-19
12622,01-Sep-14,28-Jun-19
12623,01-Sep-14,28-Jun-19

As per my soloution above I know I would need to replace the nulls with tommorows date to be able to do time intelligence on it. The reason I say tommorows date and not todays is that this table is loaded daily at 6am and so in the unlikely event that someone loads the output report between midnight and 6am the student would have left the previous day. That made sense to me but I'm not sure if it was patiularly clear.

I only need to return a count of students on roll at a paticular time so for example if I were to do a count of students on roll today from this data I would get 6 as they are null values and so have not left. I would want this to be able to answer that question at any given date.

The logic in my head is this: If the selecte date is between DoA and Leaving date then count as 1 else count as 0. This would enable me to do a trend line showing count of students over time.