查询以从表中选择时间间隔

Question

我有一个定义时间间隔的表。

_______________________________ 
| id | description | start_date | 
|____|_____________|____________| 
| 1 | First  | NULL | 
| 3 | Third  | 2009-12-18 | 
| 5 | Second  | 2009-10-02 | 
| 4 | Last  | 2009-12-31 | 
|____|_____________|____________| 

它只存储开始日期，结束日期是下一个日期之前的一天。

我想有下一个结果：

____________________________________________ 
| id | description | start_date | end_date | 
|____|_____________|____________|____________| 
| 1 | First  | NULL | 2009-10-01 | 
| 5 | Second  | 2009-10-02 | 2009-12-17 | 
| 3 | Third  | 2009-12-18 | 2009-12-30 | 
| 4 | Last  | 2009-12-31 | NULL | 
|____|_____________|____________|____________| 

我应该怎么写这个查询，因为行包含从其他行的值？

（我认为MySQL的函数DATE_SUB可能是有用的。）

Answer 1

SELECT d.id, d.description, MIN(d.start_date), MIN(d2.start_date) - INTERVAL 1 
DAY AS end_date 
FROM start_dates d 
LEFT OUTER JOIN start_dates d2 ON (d2.start_date > d.start_date OR d.start_date IS NULL) 
GROUP BY d.id, d.description 
ORDER BY d.start_date ASC 

Answer 2

如果你正在使用PHP，只是计算脚本中的一个日期。这很容易。

如果没有，会是这样的：

SELECT ID,description,start_date,start_date-1 AS end_date FROM ... 

工作？

UPDATE：它的工作原理部分，因为它返回20091224的开始日期2009-12-25但对于像日期2009-12-01等

Answer 3

将无法​​正常工作尝试

Select d.Id, d.Description, d.Start_Date, 
     n.Start_Date - 1 EndDate 
    From Table d 
    Left Join Table n 
     On n.Start_Date = 
       (Select Min(Start_date) 
       From Table 
       Where Start_Date > Coalesce(d.Start_Date, '1/1/1900') 

Answer 4

尝试

select id, description, start_date, end_date from 
    (
    select @rownum_start:=@rownum_start+1 rank, id, description, start_date 
    from inter, (select @rownum_start:=0) p 
    order by start_date 
) start_dates 
left join 
    (
    select @rownum_end:=@rownum_end+1 rank, start_date - interval 1 day as end_date 
    from inter, (select @rownum_end:=0) p 
    where start_date is not null 
    order by start_date 
) end_dates 
using (rank) 

其中inter是你的表

这实际上返回：

mysql> select id, description, start_date, end_date from ... 
+----+-------------+------------+------------+ 
| id | description | start_date | end_date | 
+----+-------------+------------+------------+ 
| 1 | First  | NULL  | 2009-10-01 | 
| 5 | Second  | 2009-10-02 | 2009-12-17 | 
| 3 | Third  | 2009-12-18 | 2009-12-30 | 
| 4 | Last  | 2009-12-31 | NULL  | 
+----+-------------+------------+------------+ 
4 rows in set (0.00 sec)