Maybe you’d like to have a running total column in a MySQL data set so you can graph the hourly running sum of sales, for example. With MySQL, you could do something like:

mysql> SET @running_total := 0;select sum(sales) AS hour_sales, @running_total:=@running_total+ sum(sales) AS running_total, hour FROM statistics WHERE day=date(now()) GROUP BY hour;

which would produce something like:

+------------+---------------+------+
| hour_sales | running_total | hour |
+------------+---------------+------+
|         48 |            48 |    0 |
|         39 |            87 |    1 |
|         44 |           131 |    2 |
|         34 |           165 |    3 |
|         61 |           226 |    4 |
|         61 |           287 |    5 |
|        122 |           409 |    6 |
|        190 |           599 |    7 |
|        209 |           808 |    8 |
|        204 |          1012 |    9 |
|         98 |          1110 |   10 |
+------------+---------------+------+
11 rows IN SET (0.00 sec)
 
mysql>

thx jay pipes