我试图平均某些特定行的值,但总计所有行的总和.
我有2个表,一个叫exchanges,另一个叫valid_country.
交流
+-----------+----------+--------------+----------+--------+
| id | ref | country | value | volume |
+-----------+----------+--------------+----------+--------+
| 1 | 1029 | DE | 1 000 | 100 |
+-----------+----------+--------------+----------+--------+
| 2 | 1029 | US | 2 000 | 250 |
+-----------+----------+--------------+----------+--------+
| 3 | 1029 | FR | 3 500 | 300 |
+-----------+----------+--------------+----------+--------+
| 4 | 1053 | UK | 1 200 | 110 |
+-----------+----------+--------------+----------+--------+
| 5 | 1029 | RU | 900 …