你的公式是累加和。下面是一个完整的示例：

SELECT rowid, a, SUM(c0) OVER(ORDER BY rowid) as c
  FROM
  (
    SELECT rowid, a, a - LAG(a, 1) OVER(ORDER BY rowid) as c0
    FROM
    (
      SELECT 1 as rowid, 5 as a union all
      SELECT 2 as rowid, 6 as a union all
      SELECT 3 as rowid, 5 as a union all
      SELECT 4 as rowid, 7 as a union all
      SELECT 5 as rowid, 8 as a union all
      SELECT 6 as rowid, 3 as a
    )t
  )t

看来可乐只是可乐减去第一排的可乐。
例如

1 = 6-5,
0 = 5-5,
2 = 7-5,
3 = 8-5,
-2 = 3-5

所以这个查询应该可以：

SELECT colA, colA - FIRST(colA) OVER (ORDER BY id) AS colC