您可以按使用的日期列对其进行分组，如果需要多天，可以添加 dateofbooking >= some_start_date 以及 dateofbooking <= some_end_date ```
"SELECT count(id) AS total FROM participant where dateofbooking='$datepick' group by dateofbooking";

倍数可能看起来像

"SELECT count(id) AS total FROM participant where dateofbooking>='$datepickstart' AND dateofbooking<='$datepickend' group by dateofbooking";

你可以用 between . 请参见下面的示例：

SELECT count(id) AS total FROM participant where dateofbooking between cast(  GETDATE() as Date) and Cast(DATEADD(DAY,-5, GETDATE()) as DATE)
Group by CAST( dateofbooking AS DATE)

另外，使用 group by Date .
注意：这不是mysql的解决方案。它适用于sql server。

你可以用 DATE_ADD() :

SELECT dateofbooking, count(id) AS total 
FROM participant 
WHERE dateofbooking >= $datepick AND 
      dateofbooking <= DATE_ADD($datepick, INTERVAL 5 DAY)
GROUP BY dateofbooking;