MySql平均值和按用法分組

Question

報告表

+----+-------------------+--------+---------------------+
| id | mac_address       |quantity| zaman               |
+----+-------------------+--------+---------------------+
| 12 | 26-C0-B7-1E-7A-8C |   001  | 2017-12-07 10:22:09 |
| 14 | 26-C0-B7-1E-7A-8C |   001  | 2017-12-07 10:28:44 |
| 15 | 26-C0-B7-1E-7A-8D |   001  | 2017-12-07 10:44:54 |
| 19 | 26-C0-B7-1E-7A-AC |   001  | 2017-12-08 10:11:00 |
| 20 | 26-C0-B7-1E-7A-AD |   002  | 2017-12-08 10:32:12 |
| 24 | 26-C0-B7-1E-7A-8D |   001  | 2017-12-09 10:29:54 |
| 25 | 26-C0-B7-1E-7A-8E |   002  | 2017-12-09 10:39:11 |

我想根據這個等式找到天數之間的平均數量：

Sum of quantity(9)/Number of day(3) = 3

---

到目前為止，我有這個查詢：

SELECT ROUND(AVG(quantity),2) AS quantity, DATE(zaman) as DateOnly 
FROM report WHERE DATE(zaman) BETWEEN ? AND ? 
GROUP BY DateOnly

我怎樣才能做到這一點？

Answer 1

嘗試使用數量之和除以天數

select sum(quantity) /( datediff(max(zaman), min(zaman))) as quantity 

FROM report WHERE DATE(zaman) BETWEEN ? AND ? 

Answer 2

嘗試這個：

SELECT ROUND((SUM(Quantity)*1.0)/datediff(MAX(Zaman), MIN(Zaman)),0)
FROM report 
WHERE zaman BETWEEN ? AND ?