Question

表名称为用户

ID | name  | created_at 
------------------------------------------
 1 | John  | 2018-11-08 14:06:05 
 2 | Adam  | 2018-12-12 10:06:05
 3 | Peter | 2019-01-08 17:16:05 
-------------------------------------------

我如何获得最近30天内每天（使用mysql或php或两者兼有）有多少新用户。结果应如下所示：

1-Sat  15
2-Sun  08
.
.
.
30-Fri 13

如果当天没有记录，则显示0。

我尝试过但是被卡住了：

select date_format(created_at,\'%a\') as day  
from users 
where datediff (now(),created_at) <=30

非常感谢

Answer 1

这是3个步骤的解决方案：

生成最近30天的列表（请在此处查看详细解决方案：Select last 30 days in MySQL
使用GROUP BY每天生成注册数量。这是SQL数据库中的关键概念，因此如果您定期使用SQL，我邀请您学习它：SQL Group By
使用LEFT JOIN将所有日期保留在日历中，并将它们与注册数量相关联。如果一天没有注册，该值将为NULL，因此在这种情况下，我使用COALESCE返回0

完整查询：

SELECT calendar.day, COALESCE(daily_registrations.nb_created, 0)
FROM
( 
    SELECT DATE_FORMAT(m1, '%a %d %M') AS day
    FROM (
        SELECT SUBDATE( NOW() , INTERVAL 30 DAY) + INTERVAL m DAY AS m1
        FROM (
            select @rownum:=@rownum+1 as m from
            (select 1 union select 2 union select 3 union select 4) t1,
            (select 1 union select 2 union select 3 union select 4) t2,
            (select 1 union select 2 union select 3 union select 4) t3,
            (select 1 union select 2 union select 3 union select 4) t4,
            (select @rownum:=-1) t0
            ) d1
    ) d2 
    WHERE m1 <= now()
    ORDER BY m1
) calendar
LEFT JOIN 
(
    SELECT date_format(created_at,'%a %d %M') AS day, COUNT(*) AS nb_created
      FROM users
     WHERE datediff (now(),created_at) <=30
     GROUP BY day
) 
daily_registrations
ON calendar.day = daily_registrations.day

PHP + Mysql-获取最近30天的每一天的统计信息

1 个答案: