将 SQL 递归限制为每次递归单行

Question

我有两个表：

事件（EventId INT，StartDate DATETIME）

 EventId | StartDate
-----------------------------
 1000    | 2021-04-05 20:32:00

原因（CauseId INT、EventId INT、分钟 INT）

 CauseId | EventId | Minutes
-----------------------------
 5000    | 1000    | 20
 5001    | 1000    | 27
 5002    | 1000    | 30

对于 EventId 和 CauseId 的每个组合，我需要生成一个 StartDate 和 EndDate。

 EventId | CauseId | Minutes | StartDate           | EndDate
------------------------------------------------------------------
 1000    | 5000    | 20      | 2021-04-05 20:32:00 | 2021-04-05 20:52:00
 1000    | 5001    | 27      | 2021-04-05 20:52:00 | 2021-04-05 21:19:00
 1000    | 5002    | 30      | 2021-04-05 21:19:00 | 2021-04-05 21:49:00

LAG 似乎行不通，我需要参考前面的行计算来生成 StartDate 和相同的行计算来生成 EndDate。

-- Not allowed.
SELECT e.EventId, c.CauseId, c.Minutes,
       LAG(CalculatedEndDate, 1, DATEADD(MI, c.Minutes, e.StartDate)) OVER (PARTITION BY e.EventId ORDER BY c.CauseId) AS CalculatedStartDate,
       DATEADD(MI, c.Minutes, CalculatedStartDate) AS CalculatedEndDate
FROM Event e
INNER JOIN Cause c ON c.EventId = e.EventId

递归 CTE 似乎也不起作用，我不允许使用 TOP 或 AGGREGATE 并且不知道如何一次处理一行它。例如

-- Initial query
UNION ALL
-- Removed for brevity
INNER JOIN cte ON cte.EventId = e.EventId
INNER JOIN Cause c ON c.CauseId  = (SELECT MIN(CauseId) FROM Cause WHERE CauseId > cte.CauseId AND EventId = e.EventId)

或

-- Initial query
UNION ALL
-- Removed for brevity
INNER JOIN cte ON cte.EventId = e.EventId
CROSS APPLY (SELECT TOP 1 *
             FROM Cause
             WHERE EventId = e.EventId AND CauseId > cte.CauseId
             ORDER BY CauseId ASC) c

Answer 1

也许 window 函数 sum() over() 会有所帮助

示例或dbFiddle

Select A.*
      ,StartDate = dateadd(MINUTE
                          ,sum(minutes) over (partition by A.EventID order by A.CauseID rows unbounded preceding ) 
                           - A.Minutes
                          ,B.StartDate)
     ,EndDate    = dateadd(MINUTE
                          ,sum(minutes) over (partition by A.EventID order by A.CauseID rows unbounded preceding ) 
                          ,B.StartDate)
 From Cause A
 Join Event B on A.EventID=B.EventID

结果

CauseId EventId Minutes StartDate               EndDate
5000    1000    20      2021-04-05 20:32:00.000 2021-04-05 20:52:00.000
5001    1000    27      2021-04-05 20:52:00.000 2021-04-05 21:19:00.000
5002    1000    30      2021-04-05 21:19:00.000 2021-04-05 21:49:00.000

将 SQL 递归限制为每次递归单行

Limit SQL recursion to single row per recursion

sql

sql-server

recursive-query