Question

我有一个项目数据集。项目从头到尾更改状态，状态更改的日期记录在表中（表名为＆＃34;事件＆＃34; - 不是我的选择）。看起来像这样（简化）：

Date        Status
2015-06-01  Start
2015-06-03  Stage 2
2015-06-07  Stage 3

在任何给定的日期范围内（动态确定）我希望能够看到哪些项目处于哪种状态。但是，对数据使用BETWEEN或其他查询只会提取那段期间已更改的项目，而不是那些仍处于给定状态的项目。

我目前在Excel中创建了一个非常笨重的解决方案，它将行复制到状态更改日期之间的新行中，如下所示：

Date          Status  
2015-06-01    Project start
2015-06-02    Project start (copied)
2015-06-03    Stage 2 
2015-06-04    Stage 2 (copied)
2015-06-05    Stage 2 (copied)
2015-06-06    Stage 2 (copied)
2015-06-07    Stage 3

此解决方案允许我查询项目的状态，例如2015-06-06，并看到它仍处于第2阶段。

有什么方法可以使用mySql来提取相同的数据，但作为输出查询？我听说有人建议使用日历表，但我不确定这是怎么回事。我也看到有人推荐过Cross Join，但我再也不能从描述中理解它是如何工作的。

提前感谢您的帮助！

Answer 1

<强>计划

通过在日历期间交叉加入数字和date_add来创建日历表。

将您的数据加入日历来源，日期为＆lt; = calendar date

取最大日期＆lt; =日历日期

加入原始数据源以获取状态

<强>设置

drop table if exists calendar_t;
CREATE TABLE calendar_t (
  id integer primary key auto_increment not null,
  `date` date not null,
  day varchar(9) not null,
  month varchar(13) not null,
  `year` integer not null
);

drop view if exists digits_v;
create view digits_v
as
select 0 as n
union all
select 1
union all
select 2
union all
select 3
union all
select 4
union all
select 5
union all
select 6
union all
select 7
union all
select 8
union all
select 9
;

insert into calendar_t
( `date`, day, month, `year` )
select 
date_add('2015-01-01', interval 100*a2.n + 10*a1.n + a0.n day) as `date`,
dayname(date_add('2015-01-01', interval 100*a2.n + 10*a1.n + a0.n day)) as day,
monthname(date_add('2015-01-01', interval 100*a2.n + 10*a1.n + a0.n day)) as month,
year(date_add('2015-01-01', interval 100*a2.n + 10*a1.n + a0.n day)) as `year`
from
digits_v a2
cross join digits_v a1
cross join digits_v a0
order by date_add('2015-01-01', interval 100*a2.n + 10*a1.n + a0.n day)
;

drop table if exists example;
create table example
(
  `date` date not null,
  status varchar(23) not null
);

insert into example
( `date`, status )
values
( '2015-06-01',  'Start'   ),
( '2015-06-03',  'Stage 2' ),
( '2015-06-07',  'Stage 3' )
;

<强>查询

select cal_date, mdate, ex2.status
from
(
select cal_date, max(ex_date) as mdate
from
(
select cal.`date` as cal_date, ex.`date` as ex_date
from calendar_t cal
inner join example ex
on ex.`date` <= cal.`date`
) maxs
group by cal_date
) m2
inner join example ex2
on m2.mdate = ex2.`date`
-- pick a reasonable end date for filtering..
where cal_date <= date('2015-06-15')
order by cal_date
;

<强>输出

+------------------------+------------------------+---------+
|        cal_date        |         mdate          | status  |
+------------------------+------------------------+---------+
| June, 01 2015 00:00:00 | June, 01 2015 00:00:00 | Start   |
| June, 02 2015 00:00:00 | June, 01 2015 00:00:00 | Start   |
| June, 03 2015 00:00:00 | June, 03 2015 00:00:00 | Stage 2 |
| June, 04 2015 00:00:00 | June, 03 2015 00:00:00 | Stage 2 |
| June, 05 2015 00:00:00 | June, 03 2015 00:00:00 | Stage 2 |
| June, 06 2015 00:00:00 | June, 03 2015 00:00:00 | Stage 2 |
| June, 07 2015 00:00:00 | June, 07 2015 00:00:00 | Stage 3 |
| June, 08 2015 00:00:00 | June, 07 2015 00:00:00 | Stage 3 |
| June, 09 2015 00:00:00 | June, 07 2015 00:00:00 | Stage 3 |
| June, 10 2015 00:00:00 | June, 07 2015 00:00:00 | Stage 3 |
| June, 11 2015 00:00:00 | June, 07 2015 00:00:00 | Stage 3 |
| June, 12 2015 00:00:00 | June, 07 2015 00:00:00 | Stage 3 |
| June, 13 2015 00:00:00 | June, 07 2015 00:00:00 | Stage 3 |
| June, 14 2015 00:00:00 | June, 07 2015 00:00:00 | Stage 3 |
| June, 15 2015 00:00:00 | June, 07 2015 00:00:00 | Stage 3 |
+------------------------+------------------------+---------+

<强> sqlfiddle

<强>参考

Answer 2

您不需要创建包含所有日期的表格。您可以更改表格以给出每个状态的开始和结束日期，并使用之间的语句。

或使用您现有的数据。

使用@datequery作为您想要查找状态的日期。

Select top 1 Status from Events
where Date <= @datequery and Date 
order by Date desc

在您查询之前返回最近的状态更改。

@datequery = 2015-06-06

Status
Stage 2

MySQL填写给定状态的两个日期之间缺少日期

2 个答案: