如何计算MySQL表中SUM的上一行和当前行的值？

Question

我的表是“ Activity_table”，其中有4列。 如何创建一个函数，每个Peroson 2先前和当前活动的总和？ 我的Activity_table

ID  PID AID Act
1   1   1   12
2   1   2   32
3   2   1   5
4   1   3   21
5   2   2   12
6   2   3   19
7   1   4   11
8   2   4   6

PID-是PersonID; AID-ActivitieID; 行为价值

我的目标：

ID  PID AID Act SUM
1   1   1   12  12
2   1   2   32  44
3   2   1   5   5
4   1   3   21  65
5   2   2   12  17
6   2   3   19  36
7   1   4   11  64
8   2   4   6   37

SUM1 = 12; SUM2 = 32 + 12; SUM3 = 5; SUM4 = 21 + 32 + 12; Sum5 = 12 + 5; Sum6 = 19 + 12 + 5; Sum7 = 11 + 21 + 32; Sum8 = 6 + 19 + 12; 谢谢，

Answer 1

要使用前两行和当前行，

SELECT ID,PID,AID,Act,
    (SELECT SUM(Act) 
     FROM Activity_table 
     WHERE ID <= a.ID
     AND ID >= a.ID - 2
     AND PID = a.PID) 
FROM Activity_table a;

Answer 2

您是根据PID对SUM进行计算吗？ 然后，目标的最后两行应修改为：

7   1   4   11  **76**
8   2   4   6   **42**

最灵活的查询是您的要求，

SELECT ID,PID,AID,Act,
    (SELECT SUM(Act) 
     FROM Activity_table 
     WHERE ID <= a.ID
     AND PID = a.PID) 
FROM Activity_table a;

然后，如果您只需要特定PID的SUM流程，则可以像这样更改它，

SELECT ID,PID,AID,Act,
    (SELECT SUM(Act) 
     FROM Activity_table 
     WHERE ID <= a.ID
     AND PID = a.PID) 
FROM Activity_table a
WHERE PID = 2;

结果：

ID  PID AID Act SUM
3   2   1   5   5
5   2   2   12  17
6   2   3   19  36
8   2   4   6   42

Answer 3

对不起，以前的答案不正确（已删除）。 这将根据您的示例产生正确的答案：

SET @LastPID = 0, @Act1 = 0,@Act2 = 0,@Act3 = 0;
SELECT ID,PID,AID,Act,`SUM` FROM 
    (
    SELECT ID,PID,AID,Act,@Act3 := IF(@LastPID != PID, 0,@Act2),@Act2 := IF(@LastPID != PID, 0,@Act1), @Act1 := Act, @Act1 + @Act2 + @Act3 `SUM`, @LastPID := PID
    FROM Activity_table
    ORDER BY PID,ID
    ) sm
ORDER BY ID
;