MySQL Running Total

gistfile1.sql

For example when I have table:

Id|Val
1 | 1
2 | 2
3 | 3
4 | 4

I'd like to get result like this:

Id|Val
1 | 1
2 | 3 # 1+2
3 | 6 # 1+2+3
4 | 10 # 1+2+3+4

You can do this by joining the table on itself. The SUM will add up all rows up to this row:

select cur.id, sum(prev.val)
from TheTable cur
left join TheTable prev
    on cur.id >= prev.id
group by cur.id

MySQL also allows the use of user variables to calculate this, which is more efficient but considered something of a hack:

select 
     id
,    @running_total := @running_total + val AS RunningTotal
from TheTable

---

To get the first row where the sum of all the previous cash is greater than a certain value, use:

SELECT y.id, y.cash
  FROM (SELECT t.id,
               t.cash,
               (SELECT SUM(x.cash)
                  FROM TABLE x
                 WHERE x.id <= t.id) AS running_total
         FROM TABLE t
     ORDER BY t.id) y
 WHERE y.running_total > 500
ORDER BY y.id
   LIMIT 1

Because the aggregate function occurs in a subquery, the column alias for it can be referenced in the WHERE clause.