MySQL选择自和>；=3.

表:

我需要选择

SUM（CASE WHEN event='+1'然后1 ELSE 0 END）

因为

SUM（CASE WHEN event='pt'然后1 ELSE 0 END）=3

我试过这个：

+++++++++++++++++++++++++
+ id | event | group_id +
+  1 |  '+1' |        1 +
+  2 |  'pt' |        1 +
+  3 |  'pt' |        1 +
+  4 |  '+1' |        1 +
+  5 |  'pt' |        1 +
+  6 |  '+1' |        1 +
+  7 |  'pt' |        1 +
+  8 |  '+1' |        1 +
+++++++++++++++++++++++++

但这不是组函数的工作方式，所以我如何实现这个输出呢？当条件

SUM（事件='pt'然后1 ELSE 0 END）=3

为真时，是否需要使用用户变量来选择id？我相信这是可能的，没有用户变量，这是可能的吗

期望输出：

SELECT group_id, SUM(CASE WHEN event = '+1' THEN 1 ELSE 0 END) AS event_sum
FROM Table
WHERE SUM(CASE WHEN event = 'pt' THEN 1 ELSE 0 END) >= 3
ORDER BY id
GROUP BY group_id

---

您需要所有+1事件的数量，因为您至少获得3个“pt”事件

对于'since'，我猜您希望按ID排序事件

对于pt，您需要一个运行总数。为了在MySQL中实现这一点，有几个关于堆栈溢出的答案（只有一个）

但您希望在每次更改groupid时重置计数，因此：

SET @pts:=0;
SELECT
   *,
   (@pts := @pts + (CASE WHEN event='pt' THEN 1 ELSE 0)) AS pts
FROM Table 
ORDER BY id;

因此，在每个循环中保存当前的groupid值，但在执行此操作之前，请检查它是否相同。如果不是，那么您可以将pts计数设为零

SET @pts:=0,@gid:=-1;
SELECT *,
    (@pts := IF (@gid != groupid, 0, @pts + IF(event='pt', 1, 0))) AS pts, 
    @gid:=groupid
FROM eventi ORDER BY groupid, id;

从这里可以看到，实际pts’的数量减少了1（检查的顺序与增量相反）

现在您可以进行分组：

+------+-------+---------+------+---------------+
| id   | event | groupid | pts  | @gid:=groupid |
+------+-------+---------+------+---------------+
|    1 | pt    |       1 |    0 |             1 |
|    2 | pt    |       1 |    1 |             1 |
|    3 | +1    |       1 |    1 |             1 |
|    4 | pt    |       1 |    2 |             1 |
|    5 | +1    |       1 |    2 |             1 |
|    6 | +1    |       1 |    2 |             1 |
|    7 | pt    |       2 |    0 |             2 |
|    8 | pt    |       2 |    1 |             2 |
|    9 | +1    |       2 |    1 |             2 |
|   10 | pt    |       2 |    2 |             2 |
|   11 | +1    |       2 |    2 |             2 |
|   12 | +1    |       2 |    2 |             2 |
+------+-------+---------+------+---------------+

也可以在同一查询中合并集合：

SET @pts:=0,@gid:=-1; 
SELECT groupid, SUM(IF(pts >= 3 AND event='+1', 1,0)) AS event_sum FROM (
    SELECT *,
       (@pts := IF(@gid!=groupid, 0, @pts+IF(event='pt',1,0)))+1 AS pts,
       @gid:=groupid
    FROM eventi ORDER BY groupid, id 
) AS a GROUP BY groupid;


+---------+-----------+
| groupid | event_sum |
+---------+-----------+
|       1 |         2 |
|       2 |         2 |
+---------+-----------+

---

这是一个。

首先求和，其中event=pt标记为temp表，然后从temp中选择并计数，其中event>=3

SET @pts:=0,@gid:=-1; 
SELECT groupid, SUM(IF(pts >= 3 AND event='+1', 1,0)) AS event_sum FROM (
    SELECT *,
       (@pts := IF(@gid!=groupid, 0, @pts+IF(event='pt',1,0)))+1 AS pts,
       @gid:=groupid
    FROM eventi ORDER BY groupid, id 
) AS a GROUP BY groupid;


+---------+-----------+
| groupid | event_sum |
+---------+-----------+
|       1 |         2 |
|       2 |         2 |
+---------+-----------+

SELECT ...  AS a, (SELECT @pts:=0,@gid:=-1) AS i GROUP BY groupid;