Mysql 按两列分组统计记录

我试图计算每个

fk_id

有多少个

amount

变量。如果存在多个变体，则我希望返回该记录，否则我希望忽略该记录

下面的陈述有什么错

SELECT *, count(fk_id) AS `count` FROM table
WHERE count > 1
GROUP BY fk_id, amount;

表:

+-----------+----------+--------------+
| id        | fk_id    | amount       |
+-----------+----------+--------------+
|         1 | 100      | 5            |
|         2 | 200      | 10           |
|         3 | 200      | 10           |
|         4 | 200      | 10           |
|         5 | 200      | 15           |
+-----------+----------+--------------+

预期产出：

+-----------+----------+--------------+--------------+
| id        | fk_id    | amount       | count        |
+-----------+----------+--------------+--------------+
|         2 | 200      | 10           | 2            |
+-----------+----------+--------------+--------------+

---

不能在

WHERE

子句中使用聚合函数。改用

HAVING

子句：

SELECT MIN(id) as id,fk_id,amount, count(fk_id)-1 AS `count` 
FROM table
GROUP BY fk_id, amount
HAVING count(fk_id)>1

结果:

ID  FK_ID   AMOUNT  COUNT
2   200     10      2

请参阅中的结果