I have a table like this:
我有一张这样的桌子:
+-----------+------------+---------------+-------------+--------------+
| member_id | balance | amount | new_balance | time |
+-----------+------------+---------------+-------------+--------------+
| 5 | 630 | -30 | 600 | 2017-08-14 |
| 3 | 142 | -68 | 74 | 2017-08-14 |
| 3 | 120 | 22 | 142 | 2017-08-13 |
| 3 | 0 | 120 | 120 | 2017-08-12 |
| 20 | 300 | 324 | 624 | 2017-08-12 |
| 4 | 100 | -30 | 70 | 2017-08-11 |
| 4 | 0 | 100 | 100 | 2017-08-10 |
| 5 | 30 | 600 | 630 | 2017-08-10 |
+-----------+------------+---------------+-------------+--------------+
+-----