每天创建的平均行数？

Question

示例表结构:

+-------------------------+---------------+------+-----+-----------------------+-----------------------------+
| Field                   | Type          | Null | Key | Default               | Extra                       |
+-------------------------+---------------+------+-----+-----------------------+-----------------------------+
| id                      | char(25)      | NO   | PRI | NULL                  |                             |
| created_at              | timestamp     | NO   |     | CURRENT_TIMESTAMP     | on update CURRENT_TIMESTAMP |
+-------------------------+---------------+------+-----+-----------------------+-----------------------------+

如何找出每天添加的平均行数？

Answer 1

这将返回一个int数字:

select count(*) / count(distinct date(created_at))
from your_table

要获得一个decimal数字使用:

select count(*) * 1.0 / count(distinct date(created_at))
from your_table

Answer 2

SELECT AVG(rowsPerDay) AS avgPerDay
FROM ( SELECT 
         COUNT(*) AS rowsPerDay
       FROM tbl
       GROUP BY DATE(created_at)
     ) AS a
;