Cumulative Sum by distinct contact_ID by year-month I've seen some posts here regarding the SUM OVER function to calculate the cumulative sum. But the issue which I have is slightly different. I need to keep a running total of distinct inactive clients by year-month. So far I've created the query to give the result as:

date       InactiveClients  TotalInactiveClients
2016-04    91954             91954
2016-03    90065             182019 &lt;-- sums 2016-04 and 2016-03
2016-02    84517             266536 &lt;-- but in past 3 months i had around 80k of inactivity
2016-01    101561            368097
2015-12    113953            482050
2015-11    85425             567475
2015-10    95681             663156
2015-09    80503             743659
2015-08    82327             825986
2015-07    96672             922658
2015-06    84375             1007033
2015-05    83740             1090773
2015-04    96933             1187706
2015-03    68572             1256278


The query is which gives me the result is here:

SELECT
      Date_FORMAT(pq.date, "%Y-%m") date,
      pq.InactiveClients as 'InactiveClients',
      @runBal := @runBal + pq.InactiveClients as TotalInactiveClients
  FROM ( SELECT 
           distinct ss1.time date, 
           COUNT(DISTINCT c1.id) as InactiveClients
         FROM `contacts` c1, `statengineSent` ss1
           LEFT JOIN `statengineViews` AS sv1 
             ON (sv1.email = ss1.email 
             AND sv1.dispatchID = ss1.dispatchID 
             AND sv1.email is NULL)
         WHERE ss1.email = c1.email 
           AND ss1.time &gt; DATE_SUB(now(), interval 13 MONTH)
         GROUP BY YEAR(date), MONTH(date)
         ORDER BY date desc ) pq,
      ( select @runBal := 0 ) sqlvars


PS: in case you are wondering with the following LEFT JOIN I am excluding all the active contacts.

LEFT JOIN `statengineViews` AS sv1 
  ON (sv1.email = ss1.email 
  AND sv1.dispatchID = ss1.dispatchID 
  AND sv1.email is NULL)
WHERE ss1.email = c1.email 
  AND ss1.time &gt; DATE_SUB(now(), interval 13 MONTH)


I need help with the following:
Could anyone help me to make the result of TotalInactiveClients equal the sum of previous months unique contact IDs?
(For example 2015-03 TotalInactiveClients = uniqe count of contactIDs inbetween 2015-03 upto 2016-04. So for 2015-10 - i need all the contactID's which occurred from 2016-04 to 2015-10 (including 2015-10)).
OK since no-one seemed to reply (except for Michael Green - Thanks) i did the MySQL statement the long way. If anyone has an idea how to make it smaller or how to combine them, then please let me know:

Last months inactivity:

Select b.date , count(b.contactID) FROM
(SELECT distinct Date_FORMAT(ss1.time, "%Y-%m") as date, c1.id as ContactID
           FROM `contacts` c1, `statengineSent` ss1
           LEFT JOIN `statengineViews` AS sv1 
           ON (sv1.email = ss1.email  AND sv1.dispatchID = ss1.dispatchID AND sv1.email is NULL)
           WHERE ss1.email = c1.email 
           AND YEAR(ss1.time) = YEAR(CURRENT_DATE - INTERVAL 0 MONTH)
                   AND MONTH(ss1.time) = MONTH(CURRENT_DATE - INTERVAL 0 MONTH)
                   ORDER BY date desc)a,
(SELECT distinct Date_FORMAT(ss1.time, "%Y-%m") as date, c1.id as ContactID
           FROM `contacts` c1, `statengineSent` ss1
           LEFT JOIN `statengineViews` AS sv1 
           ON (sv1.email = ss1.email  AND sv1.dispatchID = ss1.dispatchID AND sv1.email is NULL)
           WHERE ss1.email = c1.email 
           AND YEAR(ss1.time) = YEAR(CURRENT_DATE - INTERVAL 1 MONTH)
                   AND MONTH(ss1.time) = MONTH(CURRENT_DATE - INTERVAL 1 MONTH)
                   ORDER BY date desc)b
WHERE a.ContactID = b.ContactID


The result was:

date    inactivity
2016-03 83108


2 Months ago inactivity: 

Select c.date , count(c.contactID) FROM
(SELECT distinct Date_FORMAT(ss1.time, "%Y-%m") as date, c1.id as ContactID
           FROM `contacts` c1, `statengineSent` ss1
           LEFT JOIN `statengineViews` AS sv1 
           ON (sv1.email = ss1.email  AND sv1.dispatchID = ss1.dispatchID AND sv1.email is NULL)
           WHERE ss1.email = c1.email 
           AND YEAR(ss1.time) = YEAR(CURRENT_DATE - INTERVAL 0 MONTH)
                   AND MONTH(ss1.time) = MONTH(CURRENT_DATE - INTERVAL 0 MONTH)
                   ORDER BY date desc)a,
(SELECT distinct Date_FORMAT(ss1.time, "%Y-%m") as date, c1.id as ContactID
           FROM `contacts` c1, `statengineSent` ss1
           LEFT JOIN `statengineViews` AS sv1 
           ON (sv1.email = ss1.email  AND sv1.dispatchID = ss1.dispatchID AND sv1.email is NULL)
           WHERE ss1.email = c1.email 
           AND YEAR(ss1.time) = YEAR(CURRENT_DATE - INTERVAL 1 MONTH)
                   AND MONTH(ss1.time) = MONTH(CURRENT_DATE - INTERVAL 1 MONTH)
                   ORDER BY date desc)b,
(SELECT distinct Date_FORMAT(ss1.time, "%Y-%m") as date, c1.id as ContactID
           FROM `contacts` c1, `statengineSent` ss1
           LEFT JOIN `statengineViews` AS sv1 
           ON (sv1.email = ss1.email  AND sv1.dispatchID = ss1.dispatchID AND sv1.email is NULL)
           WHERE ss1.email = c1.email 
           AND YEAR(ss1.time) = YEAR(CURRENT_DATE - INTERVAL 2 MONTH)
                   AND MONTH(ss1.time) = MONTH(CURRENT_DATE - INTERVAL 2 MONTH)
                   ORDER BY date desc)c
WHERE a.ContactID = b.ContactID AND b.ContactID = c.ContactID


The result was: 

date    inactivity
2016-02 82355


AS you can see right now i'm using 2 statements which already are very big and sloppy and also i need to run 12 different queries to get the whole year inactivity. Can anyone help me combine these or make it work as an interval for a whole year?
It does the trick but as i said, it's very sloppy :(