SQL查询按日期更改历史记录

Question

我有一个变更历史表如下

+-----+-------------+------------+------------+
| ID  | BeforeValue | AfterValue |  DateTime  |
+-----+-------------+------------+------------+
| 255 |         396 |        400 | 01/01/2017 |
| 255 |         400 |        500 | 15/08/2017 |
| 255 |         500 |        600 | 02/06/2018 |
+-----+-------------+------------+------------+

DECLARE @tabl TABLE (ID int, BeforeValue varchar(20),AfterValue varchar(20), changeDate datetime2(0));
INSERT INTO @tabl (ID, BeforeValue, AfterValue,changeDate) VALUES
(255,'396','400', '01/01/2017'),
(255,'400','500', '08/15/2017'),
(255,'500','600', '06/02/2018');
select * from @tabl

我有另一个表，其中存在交易数据，

DECLARE @output TABLE (ID int, dat datetime2(0));
INSERT INTO @output (ID, dat) VALUES
(255, '07/15/2017'),
(255, '10/29/2018'),
(255, '01/01/2015');
select * from @output

想找出给定时间段内的价值

例如输出如下

╔═════╦════════════╦══════════════╗
║ id  ║    date    ║ Desiredvalue ║
╠═════╬════════════╬══════════════╣
║ 255 ║ 15/07/2017 ║          400 ║
║ 255 ║ 29/10/2018 ║          600 ║
║ 255 ║ 01/01/2015 ║          396 ║
╚═════╩════════════╩══════════════╝

如果没有任何存储过程，可以使用SQL语句告诉我。

Answer 1

你可以使用outer apply：

select o.*, coalesce(t.aftervalue, tfirst.beforevalue) as thevalue
from @output o outer apply
     (select top (1) t.aftervalue
      from @tab t
      where t.id = o.id and t.datetime <= o.date
      order by t.datetime desc
     ) t outer apply
     (select top (1) t.beforevalue
      from @tab t
      where t.id = o.id
      order by t.datetime asc
     ) tfirst;

Answer 2

这是我将使用的方法（实际上，这是我每天在办公室使用的方法）。正如我在评论中所说，考虑其中一个值是实时数据，这是我期望它来自的地方。因此，我也为实时数据添加了一个数据集：

--Live table
DECLARE @livetabl TABLE (ID int, [Value] int); --Store numerical values as what they are, numerical data
INSERT INTO @livetabl
VALUES (255,600);
--History table
DECLARE @histtabl TABLE (ID int, BeforeValue int,AfterValue int, changeDate datetime2(0)); 
INSERT INTO @histtabl (ID, BeforeValue, AfterValue,changeDate) VALUES
(255,396,400,'20170101'),
(255,400,500,'20170815'),
(255,500,600,'20180206');

--Your other table
DECLARE @output TABLE (ID int, dat datetime2(0));
INSERT INTO @output (ID, dat) VALUES
(255, '20170715'),
(255, '20181029'),
(255, '20150101');


SELECT l.id,
       o.dat as [date],
       ISNULL(h.BeforeValue,l.[value]) AS DesiredValue
FROM @output o
     JOIN @livetabl l ON o.id = l.id
     OUTER APPLY (SELECT TOP 1
                        BeforeValue
                  FROM @histtabl oa
                  WHERE oa.id = l.id
                    AND oa.changeDate >= o.dat
                  ORDER BY oa.changeDate ASC) h;