Question

我有一个表格，显示几天内在空间网格中发生的事件，我想为网格的每个单元格选择唯一天数，以便获取事件发生的天数，这里我的表结构：

+-----+------------+------------+---------+---------+
| id  | start_date |  end_date  | id_cell |  event  |
+-----+------------+------------+---------+---------+
|   1 | 2017-03-01 | 2017-03-04 |     250 | envent1 |
|   2 | 2017-03-01 | 2017-03-04 |     251 | envent1 |
|   3 | 2017-03-01 | 2017-03-04 |     307 | envent1 |
|   4 | 2017-03-01 | 2017-03-04 |     308 | envent1 |
|   5 | 2017-03-01 | 2017-03-09 |     250 | event2  |
|   9 | 2017-02-24 | 2017-03-03 |     250 | event3  |
|  13 | 2017-02-24 | 2017-03-24 |     250 | event4  |
|  17 | 2017-02-24 | 2017-03-02 |     250 | event5  |
|  21 | 2017-01-04 | 2017-01-25 |     250 | event6  |
|  25 | 2017-03-26 | 2017-03-28 |     250 | event2  |
+-----+------------+------------+---------+---------+

例如，250为id的单元格的预期结果为51天：

2017-01-04 -> 2017-01-25 = 21 days
2017-02-24 -> 2017-03-24 = 28 days
2017-03-26 -> 2017-03-28 = 2 days

其他日期都包含在2017-02-24和2017-03-24之间，因此不必计算在内，所以21 + 28 + 2 = 51天。

我试图像这样使用DATEDIFF（）：

select datediff(max(end_date) , min(start_date) ) from cell_date where id_cell = 250

结果为83，因为它计算2017-01-25和2017-03-01之间的天数，即未发生事件的日期。

我尝试了DATEDIFF的一些请求，但我无法弄清楚如何做到这一点。有人可以帮帮我吗？提前谢谢。

Answer 1

您可以通过按cell_id分组并计算各个差异的总和来实现此目的：

Select cell_id,[other columns],Sum(datediff(days,start_date,end_date)) as Days
From my_table
group by cell_id,[other columns]

修改

根据您的需要，我认为您应该使用中间表存储个人日期（确定它不是最佳方式），将它们与您的活动结合，然后选择结果中的不同日期。这是实现它的代码

/*Your example Talbe*/ DECLARE @T TABLE(ID INT,startDate DATE,EndDate DATE,id_cell INT,evnt NVARCHAR(20) ) INSERT INTO @T VALUES (1,'2017-03-01','2017-03-04',250,'event1'), (2,'2017-03-01','2017-03-04',251,'event1'), (3,'2017-03-01','2017-03-04',307,'event1'), (4,'2017-03-01','2017-03-04',308,'event1'), (5,'2017-03-01','2017-03-09',250,'event2'), (9,'2017-02-24','2017-03-03',250,'event3'), (13,'2017-02-24','2017-03-24',250,'event4'), (17,'2017-02-24','2017-03-02',250,'event5'), (21,'2017-01-04','2017-01-25',250,'event6'), (25,'2017-03-26','2017-03-28',250,'event2') /*Table to store days: ideally get the start and end dates from your table */ DECLARE @STARTDATE DATE='2017-01-04' DECLARE @ENDDATE DATE='2017-03-28' DECLARE @DAYS TABLE(oneday DATE) WHILE @StartDate <= @endDate BEGIN INSERT INTO @days ( oneday ) SELECT @StartDate SET @StartDate = DATEADD(dd, 1, @StartDate) END /*The request */ SELECT id_cell,COUNT(DISTINCT oneday) NUMBER_OF_DAYS FROM @T t JOIN @DAYS d ON d.oneday>=t.startDate AND d.oneday<t.EndDate WHERE id_cell=250 GROUP BY id_cell

Answer 2

您可以使用max和min date和datediff来获取日期之间的差异，例如：for event

select event, datediff(max(end_date) , min(star_date) ) 
from my_table 
group by event

或yuo可以通过cell_id求和cell_id的总和

select cell_id, sum(datediff(end_date , star_date) )as  days
from my_table 
group by cell_id

或对于您的样本，您似乎需要max end_date来查找从同一天开始的某些事件

  select id_cell, sum(datediff(max_end_date, start_date)) as days 
      from ( 
      select id_cell, start_date, max(end_date) as max_end_date
      from cell_date 
      group by id_cell, start_date ) t
  group by id_cell

MySQL：选择两个日期之间的唯一天数

2 个答案: