需要来自MySql数据库的日期块数组 [英] Need an array of date blocks from MySql Database

问题描述

好的，我有一个包含StartDate和EndDate的行的数据库表.我需要做的是从中返回消耗的时间.

Ok, I have a database table of rows with a StartDate and an EndDate. What I need to do is return blocks of consumed time from that.

例如，如果我有3行，如下所示:

So, for example, if I have 3 rows as follows:

RowID  StartDate   EndDate
1      2011-01-01  2011-02-01
2      2011-01-30  2011-02-20
3      2011-03-01  2011-04-01

然后，所用时间的块如下:

then the blocks of used time would be as follows:

2011-01-01至2011-02-20和2011-03-01至2011-04-01

2011-01-01 to 2011-02-20 and 2011-03-01 to 2011-04-01

是否有一种简单的方法可以从MySql数据库中提取该数据?欢迎任何建议！

Is there an easy method of extracting that from a MySql database? Any suggestions welcome!

推荐答案

看下面的图，它表示一些重叠的时间段

Look at the diagram below which represents some overlapping time periods

X----|              |--------|         |------X
    |-------X      X------------X
                         |----|     X----|

任何连续时间段的开始或结束(用X标记)都不在任何其他时间段之内.如果我们确定这些时间，我们可以取得一些进展.

The beginning or end of any contiguous time period, marked with an X doesn't fall inside any other time period. If we identify these times we can make some progress.

此查询标识边界.

SELECT boundary FROM
(

-- find all the lower bounds
    SELECT d1.StartDate AS boundary, 'lower' as type
    FROM dates d1
    LEFT JOIN dates d2 ON ( 
        d1.StartDate > d2.StartDate
        AND 
        d1.StartDate < d2.EndDate
    )
    WHERE d2.RowId IS NULL
    GROUP BY d1.StartDate

UNION

-- find all the upper bounds
    SELECT d1.EndDate AS boundary, 'upper' as type
    FROM dates d1
    LEFT JOIN dates d2 ON ( 
        d1.EndDate > d2.StartDate
        AND 
        d1.EndDate < d2.EndDate 
    )
    WHERE d2.RowId IS NULL
    GROUP BY d1.StartDate
) as boundaries

ORDER BY boundary ASC

此查询对您的数据的结果是

The result of this query on your data is

boundry    | type
------------------
2011-01-01 | lower
2011-02-20 | upper
2011-03-01 | lower
2011-04-01 | upper

您想要的日期范围在上面显示的连续上下限之间.只需进行一些后期处理，就可以轻松找到这些内容.

The date ranges you are after are between consecutive lower and upper bounds shown abouve. With a bit of post processing, these can easily be found.

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