Question

我有2个不同的表admin_reservations和calendar_events

admin_reservation：

ID，

FULL_NAME，

reservation_date，

reservation_time

John 03.05.2011 17:00

Mary 03.06.2011 12:00

calendar_events：

ID，

用户名，

reservation_date，

reservation_time

john.boy 02.05.2011 15:00

suzie 03.05.2011 07:00

我想这样算：

03.05.2011 2

02.06.2011 1

03.06.2011 1

Answer 1

试试这个：

SELECT dt,COUNT(id) tot FROM
(
    SELECT id,full_name fn,reservation_date dt,reservation_time
    FROM admin_reservations
    UNION ALL
    SELECT id,username fn,reservation_date dt,reservation_time
    FROM calendar_events
) GROUP BY dt ORDER BY tot desc

Answer 2

我没有太多时间，但我想分享一下：

执行a（选择表格A UNION上的全部选择表格B上的所有内容）GOUP BY日期。

MySQL UNION

MySQL GROUP BY

但要小心。这不可能很快=）

Answer 3

将每个表的计数相加可能会更快，但您应该比较执行计划：

SELECT reservation_date, SUM(date_count) FROM
(
    SELECT reservation_date, COUNT(*) AS date_count
    FROM admin_reservations
    GROUP BY reservation_date
    UNION ALL
    SELECT reservation_date, COUNT(*) AS date_count
    FROM calendar_events
    GROUP BY reservation_date
) GROUP BY reservation_date

Answer 4

感谢@Marco的代码，但我修改了一些代码以便它可以工作：

SELECT dt,COUNT(*) AS tot FROM(
  (
    SELECT reservation_date AS dt
    FROM admin_reservations
  ) 
    UNION ALL    
  (
   SELECT reservation_date AS dt
   FROM calendar_events
  )
)AS foo GROUP BY dt ORDER BY dt

来自2个不同表的Count（）

4 个答案: