彙總計算天數各月在SQL

Question

我有一個表有多個列兩列是起始日期日期和結束日期。

我需要計算每個月的天數。假設我有以下數據在我的表

id | start_date | end_date  
1 04.01.2016 15.02.2016  
2 07.01.2016 22.01.2016  
3 16.05.2016 11.07.2016 

我想要的輸出如下

Month | numberOfTravelDays  
January  51  
February 15  
May   15 
June  31  
July  11 

此輸出我期待的是總旅行天數每月已經使用的數量。我無法爲此構建sql查詢。有人可以幫助我嗎？

這是我現在。並沒有完成這項工作。下面的查詢也只過濾今年的記錄（但忽略）。

select MONTH(start_date) as month, 
    COUNT(DATEDIFF(start_date, end_date)) as numberOfTravelDays 
from travel 
where YEAR(start_date) = YEAR(CURDATE()) 
group by MONTH(start_date), 
    MONTH(end_date) 

Answer 1

使用派生表：

select monstart, 
     sum(datediff(least(m.monend, t.end_date) + interval 1 day, 
        greatest(m.monstart, t.start_date) 
        ) 
      ) as days_worked 
from travel t join 
    (select date('2016-01-01') as monstart, date('2016-01-31') as monend union all 
     select date('2016-02-01') as monstart, date('2016-02-29') as monend union all 
     . . . 
    ) m 
    on t.end_date >= m.monstart and t.start_date <= m.monend 
group by monstart;