用于比较历史记录表中列中当前值和上一个值的SQL查询

Question

我有一个SQL Server 2008数据库,其中包含用于记录主表中更改的历史记录表.我需要报告'rate'列的当前(最新)值,以及与current不同的最新值.

所以,给出类似的东西:

id   | rate   | uninteresting | updated_on   | version
-----+--------+---------------+--------------+----------
123  | 1.20   | foo           | 2010-10-18   | 1500
456  | 2.10   | bar           | 2010-10-12   | 2123
123  | 1.20   | baz           | 2010-10-10   | 1499
123  | 1.10   | baz           | 2010-10-08   | 1498
456  | 2.00   | bar           | 2010-10-11   | 2122
123  | 1.00   | baz           | 2010-08-01   | 1497
456  | 2.00   | quux          | 2010-10-05   | 2121
456  | 1.95   | quux          | 2010-09-07   | 2120

我想生产:

id   | cur_rate | cur_ver | updated_on | prev_rate | prev_ver | prev_updated
-----+----------+---------+------------+-----------+----------+-------------
123  | 1.20     | 1500    | 2010-10-18 | 1.10      | 1498     | 2010-10-08
456  | 2.10     | 2123    | 2010-10-12 | 2.00      | 2122     | 2010-10-11

请注意,我正在寻找最新条目,其中费率与最近的条目不同.

我尝试了各种方法,但要么得到太多结果,要么根本没有.有什么建议？

Answer 1

有几种方法可以实现这一目标.这是一种方式

Declare @table  as table( 
id int, 
rate decimal(10,5) , 
uninteresting  varchar(10) ,
updated_on  date, 
version int )
INSERT INTO @table
VALUES 
(123  , 1.20   , 'foo     ' , '2010-10-18'   , 1500),
(456, 2.1, ' bar           ', ' 2010-10-12   ', 2123),
(123, 1.2, ' baz           ', ' 2010-10-10   ', 1499),
(123, 1.1, ' baz           ', ' 2010-10-08   ', 1498),
(456, 2, ' bar           ', ' 2010-10-11   ', 2122),
(123, 1, ' baz           ', ' 2010-08-01   ', 1497),
(456, 2, ' quux          ', ' 2010-10-05   ', 2121),
(456, 1.95, ' quux          ', ' 2010-09-07   ', 2120)


;WITH rates 
     AS (SELECT Row_number() OVER ( PARTITION BY curr.id, curr.rate ORDER BY curr.updated_on DESC) AS rn,
            curr.id, 
            curr.rate        cur_rate, 
            curr.version     cur_ver, 
            curr.updated_on, 
            previous.rate       prev_rate, 
            previous.version    prev_ver, 
            previous.updated_on prev_updated 
          FROM 
                @table curr
                LEFT JOIN @table previous
                ON curr.id = previous.id 
                   AND curr.rate <> previous.rate
                   AND curr.updated_on > previous.updated_on 

   ) 
   SELECT 
           id, 
           cur_rate, 
           cur_ver, 
           updated_on, 
           prev_rate, 
           prev_ver, 
           prev_updated 
    FROM 
           rates 
    WHERE 
           rn = 1

产生这个结果

id          cur_rate cur_ver     updated_on prev_rate prev_ver    prev_updated
----------- -------- ----------- ---------- --------- ----------- ------------
123         1.00000  1497        2010-08-01 NULL      NULL        NULL
123         1.10000  1498        2010-10-08 1.00000   1497        2010-08-01
123         1.20000  1500        2010-10-18 1.10000   1498        2010-10-08
456         1.95000  2120        2010-09-07 NULL      NULL        NULL
456         2.00000  2122        2010-10-11 1.95000   2120        2010-09-07
456         2.10000  2123        2010-10-12 2.00000   2122        2010-10-11

如果您更改rn以降低分区中的速率,例如 ( PARTITION BY curr.id ORDER BY curr.updated_on DESC) AS rn,

你得到

id          cur_rate cur_ver     updated_on prev_rate prev_ver    prev_updated
----------- -------- ----------- ---------- --------- ----------- ------------
123         1.20000  1500        2010-10-18 1.10000   1498        2010-10-08
456         2.10000  2123        2010-10-12 2.00000   2122        2010-10-11