MYSQL COUNT 结果并在按列分组时对它们进行 AVG

Question

我正在尝试选择过去 30 天每天的平均完成次数，然后取平均值。这是我的 Rundown 表的示例

RundownID | WorkOrderID | ForemanID | Completion | RundownDate
1         | 1           | 1         | 1          | 2017-10-27
2         | 2           | 1         | 1          | 2017-10-26
3         | 3           | 1         | 1          | 2017-10-20
4         | 4           | 1         | 1          | 2017-10-27
5         | 5           | 2         | 1          | 2017-10-27
6         | 6           | 2         | 1          | 2017-10-27
7         | 7           | 3         | 1          | 2017-10-25
8         | 8           | 2         | 0          | 2017-10-20

我要找的结果是

ForemanID | ForemanAvg
1         | 4
2         | 2
3         | 1

它应该获取过去 30 天内完成行的总数，并对每个唯一的 ForemanID 每天的总数进行平均。然后平均每天的总数给我最近 30 天的平均值

我知道我很接近，但我似乎无法正确配置它。这是我走了多远

SELECT
    ForemanID,
    COUNT(RundownDate) AS ForemanAvg
FROM Rundown
WHERE RundownDate > (DATE_SUB(CURDATE(), INTERVAL '30' Day))
AND Completion = 1
GROUP BY ForemanID 

结果

ForemanID | ForemanAvg
23        | 70
24        | 100
25        | 100
26        | 76
27        | 109
29        | 11

编辑:

我越来越近了。使用以下查询我得到了我想要的结果，但是由于某种原因它只给了我一个 ForemanID

SELECT 
    a.ForemanID,
    AVG(a.ForemanAvg)
FROM (SELECT
    RundownDate,
    ForemanID,
    COUNT(RundownDate) AS ForemanAvg
FROM Rundown
WHERE RundownDate > (DATE_SUB(CURDATE(), INTERVAL '30' Day))
AND Completion = 1
GROUP BY ForemanID, RundownDate ) AS a

Answer 1

以下查询应该有效:

SELECT
    ForemanID,
    count(*)/COUNT(distinct RundownDate) AS ForemanAvg
FROM Rundown
WHERE RundownDate > (DATE_SUB(CURDATE(), INTERVAL '30' Day))
AND Completion = 1
GROUP BY ForemanID;

希望对您有所帮助!