SQL查詢來獲取的列值的次數和持續時間號到達序列中的特定值

Question

我有兩列ReceivedOn（日期/時間）和速度（INT） 樣品數據看起來像下面

 ReceivedOn  | Speed 
---------------------------------------------- 
2012-11-05 06:30:00   10 
2012-11-05 06:31:00   45 
2012-11-05 06:32:00   48 
2012-11-05 06:33:00   53 
2012-11-05 06:34:00   47 
2012-11-05 06:35:00   38 
2012-11-05 06:36:00   22 
2012-11-05 06:37:00   36 
2012-11-05 06:38:00   41 
2012-11-05 06:39:00   47 
2012-11-05 06:40:00   49 
2012-11-05 06:41:00   22 
2012-11-05 06:42:00   36 

我需要組的行當速度> 40，以使所產生的輸出將是

 StartTime  | EndTime    | Count 
-------------------------------------------------------- 
2012-11-05 06:31:00  2012-11-05 06:34:00   4 
2012-11-05 06:38:00  2012-11-05 06:40:00   3 

開始時間是ReceivedOn值當速度第一次超過40，並且EndTime值在連續記錄中的連續記錄超過40時爲ReceivedOn值，Count是超過40的連續記錄的總數。

我盡我所能，但無法得到它。是否有可能得到這與SQL查詢？ 請推薦。提前致謝。

Answer 1

下面是這些問題的一般答案。 Detect consecutive items meeting particular criteria in a time series

你的具體案例似乎更容易，因爲你沒有時間差距（他希望說）。你試圖找到你的時間序列中的差距。在你的情況下，差距被定義爲> = 40的項目。所以，你正在尋找值小於40的事件序列中的差距。

下面是一個查詢，可以爲您的時間排序行號。

SELECT @RowA := @RowA + 1 AS ROWNUM, 
     ReceivedOn, Speed 
    FROM (
     SELECT ReceivedOn, Speed 
      FROM obs 
     WHERE NOT Speed >= 40 
    ) AS A 
    JOIN (SELECT @RowA := 0) AS B 

現在您使用一些嚴重的SQL猴子業務來自我加入這個序列。這是這樣的：

SELECT B.ReceivedON + INTERVAL 1 MINUTE As StartTime, 
     A.ReceivedOn - INTERVAL 1 MINUTE AS EndTime, 
     -1 + TIMESTAMPDIFF(MINUTE, B.ReceivedOn, A.ReceivedOn) AS Count 
    FROM (
     SELECT @RowA := @RowA + 1 AS ROWNUM, 
       ReceivedOn, Speed 
      FROM (
       SELECT ReceivedOn, Speed 
       FROM obs 
       WHERE NOT Speed >= 40 
       ) AS A 
      JOIN (SELECT @RowA := 0) AS B 
     ) AS A 
    JOIN (
      SELECT @RowB := @RowB + 1 AS ROWNUM, 
       ReceivedOn, Speed 
     FROM (
       SELECT ReceivedOn, Speed 
       FROM obs 
       WHERE NOT Speed >= 40 
      ) AS A 
     JOIN (SELECT @RowB := 0) AS B 
     ) AS B ON B.ROWNUM+1 = A.ROWNUM 
WHERE TIMESTAMPDIFF(MINUTE, B.ReceivedOn, A.ReceivedOn) > 1 

http://sqlfiddle.com/#!2/2cb57/24/0

這看起來真的毛茸茸的，但它只是一個加入該第一查詢到自己ON B.ROWNUM+1 = A.ROWNUM。這將查詢的結果集排成一行，從而可以比較連續的行。

這給出了你需要的結果。請注意，如果您的第一個觀察值> = 40，則此查詢將忽略第一個觀察序列。