Running Sum

A user variable can maintain a per-row cumulative sum of column values:



SET @total=0;

SELECT id, value, @total:=@total+value AS RunningSum

FROM tbl;

If your platform does not permit multiple queries per connection, and if you can tolerate the O(N²) inefficiency of a self-join, this does the same job:



SELECT c.id, c.value, d.RunningSum

FROM tbl c

JOIN (

  SELECT a.id, SUM(b.value) AS RunningSum

  FROM tbl a

  LEFT JOIN tbl b ON b.id <= a.id

  GROUP BY a.id

) d USING (id);