MySQL:如何添加指定的行

Question

示例表

+----+---------+--------+-------+
| PK | Comp    | Amount | Class |
+----+---------+--------+-------+
| A1 | Alpha   |  2.00  |  BA   |
| A1 | Alpha   |  2.00  |  BA   |
| B1 | Bravo   |  1.50  |  BA   |
| B1 | Bravo   |  1.50  |  BA   |
| C1 | Charlie |  2.00  |  BC   |
| C1 | Charlie |  2.00  |  BC   |
| D1 | Delta   |  2.20  |  BC   |
| D1 | Delta   |  2.20  |  BC   |
| D2 | Delta   |  1.70  |  BC   |
| D2 | Delta   |  1.70  |  BC   |
| E1 | Echo    |  3.10  |  BD   |
| E1 | Echo    |  3.10  |  BD   |
| E2 | Echo    |  3.00  |  BD   |
| E2 | Echo    |  3.00  |  BD   |
| E3 | Echo    |  2.90  |  BD   |
| E3 | Echo    |  2.90  |  BD   |
| E4 | Echo    |  2.50  |  BD   |
| E4 | Echo    |  2.50  |  BD   |
| E5 | Echo    |  3.10  |  BD   |
| E5 | Echo    |  3.10  |  BD   |
+----+---------+--------+-------+

我如何ADD每个PK的第一个值？我一直在用
SUM(Amount) AS TotalAmount...GROUP BY Class

结果是这样的

+----+---------+--------+-------+-------------+
| PK | Comp    | Amount | Class | TotalAmount |
+----+---------+--------+-------+-------------+
| A1 | Alpha   |  2.00  |  BA   | 7.00        |
| C1 | Charlie |  2.00  |  BC   | 11.80       |
| E1 | Echo    |  3.10  |  BD   | 29.20       |
+----+---------+--------+-------+-------------+

它添加了所有的Amount。
我使用了 SUM(MAX(Amount)) AS TopAmount 但出现了错误。
我想要这张 table

+----+---------+--------+-------+-------------+
| PK | Comp    | Amount | Class | TotalAmount |
+----+---------+--------+-------+-------------+
| A1 | Alpha   |  2.00  |  BA   | 3.50        |
| C1 | Charlie |  2.00  |  BC   | 5.90        |
| E1 | Echo    |  3.10  |  BD   | 14.6        |
+----+---------+--------+-------+-------------+  

像这样只是每个PK

的第一个数据

+-------------------+-------+-------------+
| Amount            | Class | TotalAmount |
+-------------------+-------+-------------+
| (A1+B1)           |  BA   | 3.50        |
| (C1+D1+D2)        |  BC   | 5.90        |
| (E1+E2+E3+E4+E5)  |  BD   | 14.6        |
+-------------------+-------+-------------+  

谢谢你的时间..

Answer 1

试试这个。将 t1 替换为您的表名

SELECT GROUP_CONCAT(PK SEPARATOR '+'), Class ,SUM(Amount) AS 
TotalAmount FROM 
(SELECT DISTINCT PK, Comp, Amount, Class FROM t1) AS t2  
GROUP BY Class;