sql - 此过程的游标替代方案？

Question

我有一个包含这种格式记录的表:

SPECIAL_ID | OTHER_ID | NAME | TIMESTAMP

我需要基于此创建一个新表，但只获取与前一个记录相隔至少 25 分钟的记录。间隔不一致。因此，如果我从记录 1 开始，我需要获取距离记录 1 的时间戳至少 25 分钟的下一条记录。这将是新表中的记录 2。然后是提取的前一条记录后 25 分钟的下一条记录。因此，这是一个信息示例:

AAA | 1 | WHATEVER2  | 2016-11-20 00:00:00
BCD | 2 | WHATEVER00 | 2016-11-20 00:02:00
AAA | 3 | WHATEVER01 | 2016-11-20 00:09:00
AAA | 4 | WHATEVER55 | 2016-11-20 00:20:00
XYZ | 5 | WHATEVER   | 2016-11-20 00:24:00
AAA | 6 | WHATEVER11 | 2016-11-20 00:45:00
QRS | 7 | WHATEVER   | 2016-11-20 00:46:00
QRS | 8 | WHATEVER12 | 2016-11-20 00:59:00
AAA | 9 | WHATEVER12 | 2016-11-20 01:02:00
AAA |10 | WHATEVER12 | 2016-11-20 01:17:00

我想做的是:

AAA | 1 | WHATEVER2  | 2016-11-20 00:00:00
AAA | 6 | WHATEVER11 | 2016-11-20 00:45:00
AAA |10 | WHATEVER12 | 2016-11-20 01:17:00

我设法使用游标并在一小组记录上对其进行了测试。它有效....但我有 数百万 的记录需要以这种方式进行分析。看来，游标只是自找麻烦。

有更好的方法吗？

我被 SQL Server 2008 困住了，所以 lead() 和 lag() 是不可能的。

非常感谢任何帮助。

Answer 1

对于 Sql Server 2008，这可能是一个可能的(计算成本高的)解决方案:

第一步，确定第一条记录。在第二步，查询为每个现有记录确定最近的 25 分钟记录。 随后(步骤 3)，数据记录被缩减为具有最低 OTHER_ID 的记录。当然，这只适用于 OTHER_ID 唯一且随时间同步增加的字段。 对于数百万条记录，应该对查询中使用的字段进行索引并限制搜索。

-- test script

SET dateformat ymd

;WITH testdata AS (
  SELECT 'AAA'       AS SPECIAL_ID, 
         1           AS OTHER_ID, 
         'WHATEVER2' AS NAME , 
         CONVERT(DATETIME, '2016-11-20 00:00:00') AS [TIMESTAMP]
  UNION SELECT 'BCD' , 2 , 'WHATEVER00' , CONVERT(DATETIME, '2016-11-20 00:02:00')
  UNION SELECT 'AAA' , 3 , 'WHATEVER01' , CONVERT(DATETIME, '2016-11-20 00:02:01')
  UNION SELECT 'AAA' , 4 , 'WHATEVER55' , CONVERT(DATETIME, '2016-11-20 00:20:00')
  UNION SELECT 'XYZ' , 5 , 'WHATEVER'   , CONVERT(DATETIME, '2016-11-20 00:24:00')
  UNION SELECT 'AAA' , 6 , 'WHATEVER11' , CONVERT(DATETIME, '2016-11-20 00:45:00')
  UNION SELECT 'QRS' , 7 , 'WHATEVER'   , CONVERT(DATETIME, '2016-11-20 00:46:00')
  UNION SELECT 'QRS' , 8 , 'WHATEVER12' , CONVERT(DATETIME, '2016-11-20 00:59:00')
  UNION SELECT 'AAA' , 9 , 'WHATEVER12' , CONVERT(DATETIME, '2016-11-20 01:02:00')
  UNION SELECT 'AAA' ,10 , 'WHATEVER12' , CONVERT(DATETIME, '2016-11-20 01:17:00')
  UNION SELECT 'QRS' ,11 , 'WHATEVER13' , CONVERT(DATETIME, '2016-11-20 01:30:00')
), firstRecord AS (
  SELECT SPECIAL_ID, MIN(OTHER_ID) AS OTHER_ID
    FROM testdata
   GROUP BY SPECIAL_ID
), nextRecord1 AS (
  SELECT I1.SPECIAL_ID, I1.OTHER_ID AS OTHER_ID, MIN(I2.OTHER_ID) AS next_OTHER_ID
    FROM testdata I1
         INNER JOIN testdata I2 
                 ON I1.SPECIAL_ID = I2.SPECIAL_ID 
                AND I1.OTHER_ID < I2.OTHER_ID
                AND I2.[TIMESTAMP] >= DATEADD(minute, 25, I1.[TIMESTAMP])
   GROUP BY I1.SPECIAL_ID, I1.OTHER_ID
), nextRecord2 AS (
  SELECT SPECIAL_ID, MIN(OTHER_ID) AS OTHER_ID, next_OTHER_ID
    FROM nextRecord1
   GROUP BY SPECIAL_ID, next_OTHER_ID
)
SELECT T2.*
  FROM firstRecord T1
       INNER JOIN testdata T2 
               ON T1.OTHER_ID = T2.OTHER_ID
UNION
SELECT T2.*
  FROM nextRecord2 T1
       INNER JOIN testdata T2  
               ON T1.next_OTHER_ID = T2.OTHER_ID