選擇最接近的時間戳，每30分鐘

Question

假設我在表後的時間戳數據：

Id     Timestamp 
-------------------- ----------------------- 
1     2016-09-19 13:17:24.000 
2576     2016-09-19 13:47:24.000 
4945     2016-09-19 14:17:24.000 
7538     2016-09-19 14:47:24.000 
10016    2016-09-19 15:17:24.000 
10570    2016-09-19 15:24:51.000 
11968    2016-09-19 15:47:55.000 
11990    2016-09-19 15:48:08.000 
13648    2016-09-19 16:18:08.000 
14742    2016-09-19 16:36:55.000 

現在我想從起始日期選擇最接近的時間戳並搜索發現時間戳+ 30分鐘，下一個最接近的時間戳

短例如：

start_date = 2016-09-19 13:00:00.000 
end_date = 2016-09-19 16:00:00.000 
Now it should find record: 
2016-09-19 13:17:24.000 
Now we add 30 minutes to found date, so we will search closest timestamp for 13:47:23.000 and so on until date = 16:00. 

注：應該是接近的近似值，因此它可以小於30分鐘的diff

完整的例子：

start_date = 2016-09-19 13:00:00.000 
end_date = 2016-09-19 16:00:00.000 

Id     Timestamp 
-------------------- ----------------------- 
1     2016-09-19 13:17:24.000 
2576     2016-09-19 13:47:24.000 
4945     2016-09-19 14:17:24.000 
7538     2016-09-19 14:47:24.000 
10016    2016-09-19 15:17:24.000 
11968    2016-09-19 15:47:55.000 

我怎樣才能做到這一點？我寧願避免使用光標，它可以通過

Answer 1

如果Id和Timestamp出現在相同的順序使用下面的代碼（沒有遞歸或CTE）：

SELECT * 
INTO #TempTable 
FROM (VALUES 
    (1,  CAST('2016-09-19 13:17:24.000' AS DATETIME)), 
    (2576, CAST('2016-09-19 13:47:24.000' AS DATETIME)), 
    (4945, CAST('2016-09-19 14:17:24.000' AS DATETIME)), 
    (7538, CAST('2016-09-19 14:47:24.000' AS DATETIME)), 
    (10016, CAST('2016-09-19 15:17:24.000' AS DATETIME)), 
    (10570, CAST('2016-09-19 15:24:51.000' AS DATETIME)), 
    (11968, CAST('2016-09-19 15:47:55.000' AS DATETIME)), 
    (11990, CAST('2016-09-19 15:48:08.000' AS DATETIME)), 
    (13648, CAST('2016-09-19 16:18:08.000' AS DATETIME)), 
    (14742, CAST('2016-09-19 16:36:55.000' AS DATETIME))) 
    AS T (Id, [Timestamp]) 

DECLARE 
    @StartDate DATETIME = '2016-09-19 13:00:00.000', 
    @EndDate DATETIME = '2016-09-19 16:00:00.000'; 

SELECT MIN(Id) AS Id, MIN([Timestamp]) AS [Timestamp] 
FROM #TempTable 
WHERE [Timestamp] BETWEEN @StartDate AND @EndDate 
GROUP BY 
    CAST([Timestamp] AS DATE), -- day 
    DATEPART(hour, [Timestamp]), -- hour 
    DATEPART(minute, [Timestamp])/30 -- half an hour (0 or 1) 
ORDER BY Id 

如果我們沒有這樣的排序和相同的Timestamp可以出現多次，CTE可以使用：

DECLARE 
    @StartDate DATETIME = '2016-09-19 13:00:00.000', 
    @EndDate DATETIME = '2016-09-19 16:00:00.000'; 

WITH TargetTimestamps AS 
(
    SELECT MIN([Timestamp]) AS MinTimestamp 
    FROM #TempTable 
    WHERE [Timestamp] BETWEEN @StartDate AND @EndDate 
    GROUP BY 
     CAST([Timestamp] AS DATE), -- day 
     DATEPART(hour, [Timestamp]), -- hour 
     DATEPART(minute, [Timestamp])/30 -- half an hour (0 or 1) 
) 
SELECT MIN(Id) AS Id, MinTimestamp 
FROM #TempTable 
JOIN TargetTimestamps ON [Timestamp] = MinTimestamp 
GROUP BY MinTimestamp -- use grouping to avoid duplicates for the same [Timestamp] 
ORDER BY MinTimestamp 

Answer 2

您可以在單個查詢中執行此操作。我不是100％確定你實際需要什麼（你的例子似乎在收縮聲明）。但這裏是一般結構：

with x as (
     select min(timestamp) as first_timestamp 
     from t 
     where timestamp >= @start_date 
    ) 
select t.* 
from t join 
    x 
    on t.timestamp >= x.first_timestamp and 
     t.timestamp < dateadd(minute, 30, x.first_timestamp); 

Answer 3

遞推通過

口授

下爲發現時間戳+ 30分鐘最接近時間戳

不幸CTE不允許TOP（1）遞歸部分。解決方法是使用row_number（）... = 1

SELECT * 
INTO #TempTable 
FROM (VALUES 
    (1,  CAST('2016-09-19 13:17:24.000' AS DATETIME)), 
    (2576, CAST('2016-09-19 13:47:24.000' AS DATETIME)), 
    (4945, CAST('2016-09-19 14:17:24.000' AS DATETIME)), 
    (7538, CAST('2016-09-19 14:47:24.000' AS DATETIME)), 
    (10016, CAST('2016-09-19 15:17:24.000' AS DATETIME)), 
    (10570, CAST('2016-09-19 15:24:51.000' AS DATETIME)), 
    (11968, CAST('2016-09-19 15:47:55.000' AS DATETIME)), 
    (11990, CAST('2016-09-19 15:48:08.000' AS DATETIME)), 
    (13648, CAST('2016-09-19 16:18:08.000' AS DATETIME)), 
    (14742, CAST('2016-09-19 16:36:55.000' AS DATETIME))) 
    AS T (Id, [Timestamp]) 

DECLARE 
    @StartDate DATETIME = '2016-09-19 13:00:00.000', 
    @EndDate DATETIME = '2016-09-19 16:00:00.000'; 


with found as (
    select top(1) *, r = 1 
    from #TempTable 
    where [Timestamp] between @StartDate and @EndDate 
    order by [Timestamp] 
    union all 
    select t.*, r = cast(row_number() over (partition by f.r order by t.[Timestamp]) as int) 
    from found f 
    join #TempTable t on t.[Timestamp] >= dateadd(minute, 30, f.[Timestamp]) 
     and t.[Timestamp] between @StartDate and @EndDate 
     and f.r=1 
) 
select * 
from found 
where r = 1 
order by [Timestamp]