根據與上一個記錄和下一個記錄的關係選擇刪除記錄

我有一個SQL Server 2014表，其中包含數百萬個gps座標，每個座標都在特定時間。然而，註冊之間的時間間隔並不固定，從1秒到幾個小時不等。我只想每4分鐘進行一次測量，因此其他記錄必須刪除。根據與上一個記錄和下一個記錄的關係選擇刪除記錄

我試過了遍歷每條記錄的T-SQL中的一個WHILE循環，循環內部有一個帶雙CROSS APPLY的SELECT語句，如果它位於另外兩條不超過4分鐘的記錄中，它將只返回一條記錄分開。然而這個策略太慢了。

這可以通過基於集合的解決方案來完成嗎？或者有沒有辦法加快這個查詢？（下面的測試查詢只是打印，還沒有刪除）

SELECT * INTO #myTemp FROM gps ORDER BY TimePoint asc 

declare @Id Uniqueidentifier 
declare @d1 varchar(19) 
declare @d2 varchar(19) 
declare @d3 varchar(19) 


While EXISTS (select * from #myTemp) 
BEGIN 
    select top 1 @Id = ID FROM #myTemp order by TimePoint asc 

    SELECT 
     @d1 = convert(varchar(19), a.justbefore, 121), 
     @d2 = convert(varchar(19), b.tijdstip, 121), 
     @d3 = convert(varchar(19), c.justafter, 121) 
    FROM Gps B CROSS APPLY 
     (
      SELECT top 1 TimePoint as justbefore 
      FROM Gps 
      WHERE (B.TimePoint > TimePoint) AND (B.Id = @Id) 
      ORDER by TimePoint desc 
     ) A 
     CROSS APPLY (
      SELECT top 1 TimePoint as justafter 
      FROM Gps 
      WHERE (Datediff(n,A.justbefore,TimePoint) between -4 AND 0) 
        AND (B.TimePoint < TimePoint) 
      ORDER by TimePoint asc 
     ) C 

    print 'ID=' + Cast(@id as varchar(50)) 
       + '/d1=' + @d1 + '/d2=' + @d2 + '/d3=' + @d3     

    DELETE #myTemp where Id = @id 
END

Sample data: 
    Id  TimePoint   Lat  Lon 
    1  20170725 13:05:27 12,256 24,123 
    2  20170725 13:10:27 12,254 24,120 
    3  20170725 13:10:29 12,253 24,125 
    4  20170725 13:11:55 12,259 24,127 
    5  20170725 13:11:59 12,255 24,123 
    6  20170725 13:14:28 12,254 24,126 
    7  20170725 13:16:52 12,259 24,121 
    8  20170725 13:20:53 12,257 24,125

在這種情況下，記錄3,4,5應予刪除。記錄7應保持爲7和8之間的差距超過4分鐘。

來源

2017-07-26 Jan

你能發佈一些示例數據和預期的結果？ –

我同意樣本數據和預期的結果會使這更容易通過。但我會建議做一個搜索差距和島嶼有很多例子。訣竅是你會希望將記錄分成4分鐘的增量，並能夠識別每個組中的第一條記錄。 – Matt

看着數字...它看起來像1 & 2住（相隔5分鐘）... 3，4，& 5應該去... 6次住宿（4分鐘從2）... 7應該去（僅6 2分鐘）和8個住宿（6 6分）...

If this is correct, the following will do what you're looking for... 


IF OBJECT_ID('tempdb..#TestData', 'U') IS NOT NULL 
DROP TABLE #TestData; 

CREATE TABLE #TestData (
    Id INT NOT NULL PRIMARY KEY CLUSTERED, 
    TimePoint DATETIME2(0) NOT NULL, 
    Lat DECIMAL(9,3), 
    Lon DECIMAL(9,3) 
    ); 

INSERT #TestData (Id, TimePoint, Lat, Lon) VALUES 
    (1, '20170725 13:05:27', 12.256, 24.123), 
    (2, '20170725 13:10:27', 12.254, 24.120), 
    (3, '20170725 13:10:29', 12.253, 24.125), 
    (4, '20170725 13:11:55', 12.259, 24.127), 
    (5, '20170725 13:11:59', 12.255, 24.123), 
    (6, '20170725 13:14:28', 12.254, 24.126), 
    (7, '20170725 13:16:52', 12.259, 24.121), 
    (8, '20170725 13:20:53', 12.257, 24.125); 

-- SELECT * FROM #TestData td; 

--================================================================================ 

WITH 
    cte_AddLag AS (
     SELECT 
      td.Id, td.TimePoint, td.Lat, td.Lon, 
      MinFromPrev = DATEDIFF(mi, LAG(td.TimePoint, 1) OVER (ORDER BY td.TimePoint), td.TimePoint) 
     FROM 
      #TestData td 
     ), 
    cte_TimeGroup AS (
     SELECT 
      *, 
      TimeGroup = ISNULL(SUM(al.MinFromPrev) OVER (ORDER BY al.TimePoint ROWS UNBOUNDED PRECEDING)/4, 0) 
     FROM 
      cte_AddLag al 
     ) 
SELECT TOP 1 WITH TIES 
    tg.Id, 
    tg.TimePoint, 
    tg.Lat, 
    tg.Lon 
FROM 
    cte_TimeGroup tg 
ORDER BY 
    ROW_NUMBER() OVER (PARTITION BY tg.TimeGroup ORDER BY tg.TimePoint);

結果...

Id   TimePoint     Lat          Lon 
----------- --------------------------- --------------------------------------- --------------------------------------- 
1   2017-07-25 13:05:27   12.256         24.123 
2   2017-07-25 13:10:27   12.254         24.120 
6   2017-07-25 13:14:28   12.254         24.126 
8   2017-07-25 13:20:53   12.257         24.125

HTH，傑森

來源

2017-07-26 02:50:42

理論上，第7點應該留下來，目標是儘可能接近4分鐘的距離。通過消除第7點，點6和點8之間的間隔變得超過6分鐘。 – Jan

有沒有這樣做的有效方法。 –

根據與上一個記錄和下一個記錄的關係選擇刪除記錄

回答

相關問題